UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K/A

Amendment No. 1

(Mark One)

For the fiscal year ended December 31, 2017

OR

FOR THE TRANSITION PERIOD FROM                      TO                     

Commission File Number 001-36456

ZENDESK, INC.

(Exact name of Registrant as specified in its Charter)

Registrant’s telephone number, including area code: (415) 418-7506

Securities registered pursuant to Section 12(b) of the Act: Common Stock, Par Value $0.01 Per Share; Common Stock traded on the New York Stock Exchange

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the Registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.    YES  ☒    NO  ☐

Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.    YES  ☐    NO  ☒

Indicate by check mark whether the Registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    YES  ☒    NO  ☐

Indicate by check mark whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the Registrant was required to submit such files).    YES  ☒    NO  ☐

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K (§229.405) is not contained herein, and will not be contained, to the best of Registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.  ☐

Indicate by check mark whether the Registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer”, “accelerated filer”, “smaller reporting company”, and “emerging growth company” in Rule 12b-2 of the Exchange Act. (Check one):

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act  ☐

Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    YES  ☐    NO  ☒

The aggregate market value of common stock held by non-affiliates of the Registrant, computed by reference to the price at which the common stock was last sold on June 30, 2017, the last business day of the Registrant’s most recently completed second fiscal quarter, as reported on the New York Stock Exchange, was approximately $1.8 billion. Shares of common stock held by each executive officer, director and holder of 5% or more of the outstanding common stock have been excluded in that such persons may be deemed to be affiliates. This determination of affiliate status does not reflect a determination that such persons are affiliates of the Registrant for any other purpose.

The number of shares of the Registrant’s Common Stock outstanding as of October 31, 2018 was 107,041,554.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the Registrant’s definitive Proxy Statement for its 2018 Annual Meeting of Stockholders, filed on April 3, 2018, are incorporated by reference in Part III of this Annual Report on Form 10-K. Except with respect to information specifically incorporated by reference in this Annual Report on Form 10-K, the Proxy Statement is not deemed to be filed as part of this Annual Report on Form 10-K.

EXPLANATORY NOTE

This Form 10-K/A (“Amendment No. 1”) is being filed to amend our Annual Report on Form 10-K for the fiscal year ended December 31, 2017 (“Original Filing”), filed with the U.S. Securities and Exchange Commission on February 22, 2018, to replace Exhibit 32.1 thereto with the corrected version of that exhibit submitted herewith. The original exhibit 32.1 mistakenly referenced the period covered by the Original Filing as being the year ended December 31, 2016. The correct period covered by the Original Filing is the year ended December 31, 2017.

The Company hereby amends the Original Filing by resubmitting the corrected version of Exhibit 32.1 with this Amendment No. 1 to correct this inadvertent clerical error. This Amendment No. 1 does not modify, amend or update in any way any of the financial or other information contained in the Original Filing. This Amendment No. 1 does not reflect events that may have occurred subsequent to the date of the Original Filing.

Pursuant to Rule 12b-15 of the Rules and Regulations under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), the Company has included with this Amendment No. 1 currently-dated certifications by the Company’s principal executive officer and principal financial officer, as required by Exchange Act Rules 13a-14(a) and (b).

Table of Contents

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K contains forward-looking statements within the meaning of federal securities laws, which statements involve substantial risks and uncertainties. Forward-looking statements generally relate to future events or our future financial or operating performance. In some cases, you can identify forward-looking statements because they contain words such as “may,” “will,” “should,” “might,” “expects,” “plans,” “anticipates,” “could,” “intends,” “target,” “projects,” “contemplates,” “believes,” “estimates,” “predicts,” “potential,” or “continue,” or the negative of these words or other similar terms or expressions that concern our expectations, strategy, plans, or intentions. Forward-looking statements contained in this Annual Report on Form 10-K include, but are not limited to, statements about:

We caution you that the foregoing list does not contain all of the forward-looking statements made in this Annual Report on Form 10-K.

You should not rely upon forward-looking statements as predictions of future events. We have based the forward-looking statements contained in this Annual Report on Form 10-K primarily on our current expectations and projections about future events and trends that we believe may affect our business, financial condition, operating results, and prospects. The outcome of the events described in these forward-looking statements is subject to risks, uncertainties, and other factors described in the section titled “Risk Factors” and elsewhere in this Annual Report on Form 10-K. Moreover, we operate in a very competitive and rapidly changing environment. New risks and uncertainties emerge from time to time, and it is not possible for us to predict all risks and uncertainties that could have an impact on the forward-looking statements contained in this Annual Report on Form 10-K. We cannot assure you that the results, events, and circumstances reflected in the forward-looking statements will be achieved or occur, and actual results, events, or circumstances could differ materially from those described in the forward-looking statements.

The forward-looking statements made in this Annual Report on Form 10-K relate only to events as of the date on which the statements are made. We undertake no obligation to update any forward-looking statements made in this Annual Report on Form 10-K to reflect events or circumstances after the date of this Annual Report on Form 10-K or to reflect new information or the occurrence of unanticipated events, except as required by law. We may not actually achieve the plans, intentions, or expectations disclosed in our forward-looking statements and you should not place undue reliance on our forward-looking statements. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, joint ventures, or investments we may make.

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PART I

Overview

As the rise of new communication channels and ubiquitous access to information have made customer relationships increasingly complex, we believe that expanding beyond customer service to address customer journeys more broadly matters more than ever. Customers have individual channel preferences, and they want to be recognized across any and all channels they choose. To address these trends, organizations ranging from the smallest startups to the largest businesses must deliver the best omnichannel customer experience possible, from creating a more unified customer experience to simplifying the buying experience across products.

The Zendesk product family is purpose-built to unify disparate channels and departments and to simplify the process of providing great customer service, whether that is through self-service, a phone call, live chat, messaging, or a simple email. Our product family is built upon a modern architecture that enables us and our customers to rapidly innovate, adapt our technology in novel ways, and easily integrate with other products and applications. With our origins in customer service, we have evolved our offerings over time to help even the largest organizations understand their customers, improve communications across all channels, and engage where and when it’s needed most.

We are a software development company founded in Copenhagen, Denmark in 2007. We reincorporated in Delaware in 2009. Our principal executive offices are located at 1019 Market Street, San Francisco, California 94103, and our telephone number is (415) 418-7506. Our website address is www.zendesk.com. Information contained on or that can be accessed through our website does not constitute part of this Annual Report on Form 10-K, and inclusions of our website address in this Annual Report on Form 10-K are inactive textual references only. Unless expressly indicated or the context requires otherwise, the terms “Zendesk,” “company,” “we,” “us,” and “our” in this Annual Report on Form 10-K refer to Zendesk, Inc., a Delaware corporation, and its consolidated subsidiaries.

The Zendesk Approach

We believe that building software for the customer journey first requires an approach to both product design and delivery that is unified, unique, and innovative. As software continues to evolve to become central to the customer experience, we strive to design products which are proactive, contextual, and integrated by design. We believe in developing products that serve organizations of all sizes and across all industries. Our focus on these core principles has led us to design a family of products that share the following characteristics:

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We have witnessed business software undergo a dramatic shift toward consumerization over the past decade. Zendesk has embraced this shift with an approach to delivering its family of products that is dramatically different from earlier generations of business software. Our goal is to remove barriers that make business software difficult to buy, deploy, and use. Our approach to software delivery focuses on the following key elements:

Growth Strategy

Zendesk was founded with a mission to help organizations build better relationships with their customers. We have continued to pursue that mission by focusing on building and delivering software for relationships first. We believe our future growth will be a natural extension of that mission, focusing on the following key growth drivers:

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Zendesk has always served a global market and, for the year ended December 31, 2017, we generated 47% of our revenue outside of the United States. We will continue to expand our global footprint, particularly in those markets where we have demonstrated significant customer traction with our democratized approach or which represent particularly strategic opportunities.

The Zendesk Family of Products and Developer Platform

The Zendesk family of products is built to work together to help organizations understand and improve customer relationships. Zendesk products share a common interface and are being developed to support a shared services infrastructure and common customer data platform.

Zendesk’s products are developed using agile software techniques, and are designed to quickly incorporate and innovate on customer feedback obtained through extensive Early Access Programs, or EAPs. This approach allows us to share our newest technology with customers, and quickly adapt our products to address customer needs.

Our current family of products includes:

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Zendesk’s developer platform allows organizations to extend the functionality of our family of products, integrate into internal and third-party systems, and customize the experience for their employees and customers. Key components of Zendesk’s developer platform include:

Technology

We employ a modern technology architecture in which our products are built upon a set of core APIs that enable rapid innovation and deep integration. The technology infrastructure used for the Zendesk family of products is designed to provide a highly available and scalable cloud-based platform with industry-standard security measures. The architecture and deployment of our software are described and guided by the following key characteristics:

Part of our evolving operations strategy is the continued refinement of our hosting infrastructure to optimize for reliability, performance, and cost. We provide our services through a combination of cloud infrastructure providers such as Amazon Web Services (AWS) and Google Cloud Platform and co-located managed data centers.

Customers

As of December 31, 2017, we had an aggregate of approximately 118,900 paid customer accounts using our family of products. This includes approximately 64,100 customer accounts for paid subscription plans for Zendesk Support (other than our legacy Starter plan) and approximately 47,000 customer accounts for paid subscription plans of Zendesk Chat. In addition, we had approximately 7,800 paid customer accounts on our other products, collectively, as of December 31, 2017.

Prior to purchase, we generally provide our prospective customers with the opportunity to try fully-functioning versions of our products for a free trial period. This is a central part of our business model as we believe customers should have the right to try products before being locked-into a subscription. Providing our customers with a free trial period exposes customers to our brand and establishes a relationship that can facilitate further adoption of our products as organizations grow in size and their needs become more complex.

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Our customers are located in over 160 countries and territories and represent organizations across a broad array of sizes, industries, and geographies.

Research and Development

Our research and development organization is responsible for the development, design, and testing of all aspects of our products. We invest heavily in these efforts to continuously improve and innovate. In addition to our hosted software solution, we have developed multi-functional APIs that we utilize to build our products as well as facilitate integrations of our products with third-party applications.

Our global research and development team is primarily based in San Francisco, California; Copenhagen, Denmark; Melbourne, Australia; Dublin, Ireland; Singapore; Montpellier, France; and Metro Manila, Philippines. To foster rapid innovation, our research and development team is further apportioned into smaller, agile development teams.

We deploy new features, functionality, and technologies across our products through frequent software releases or updates in order to minimize disruption and provide for constant improvement.

To create a product roadmap that meets our customers’ needs, we emphasize collaboration during the development process. Customers provide input through feedback forums, dialogue with our product support and research and development teams, and feature utilization. As a result of using our products internally to support our customers, we also develop new or improved features based on our own employees’ feedback.

As of December 31, 2017, we had approximately 530 employees in our research and development organization. Our research and development expenses were $115.3 million, $91.1 million, and $62.6 million for the years ended December 31, 2017, 2016, and 2015, respectively.

Sales and Marketing

Subscriptions to our products are designed to be easy to purchase. A substantial number of our customers subscribe to our products with limited or no direct interaction with our sales team.

We also deploy a direct sales approach, which includes a sales team based in four regional hubs: North America, LATAM (Latin America), EMEA (Europe, Middle East, and Africa), and APAC (Asia-Pacific). This team manages prospective and current customers, aiming to initiate, retain, and expand their use of our family of products over time, and is responsible for driving expansions and renewals of existing contracts. Our sales team also partners with sales and product engineers to provide pre-sales technical support to prospective customers.

We expect to continue increasing penetration into larger organizations through a land and expand strategy whereby we attempt to capitalize on the use of our products by a functional or geographic department to expand the use of our products throughout the organization. Through our sales team, we also seek to discover and work with a growing number of forward-thinking enterprises on larger initiatives to transform their approach to customer experience.

We also utilize indirect sales channels, including referral partners and resellers, as well as implementation partners. These channel partners provide additional sales coverage, particularly in geographic markets where we may have limited presence, as well as implementation services to our customers. Sales from indirect channels have not been significant to date, but we plan to continue investing in these relationships to help us in certain markets and to complement our direct sales efforts.

Our marketing efforts are focused on generating awareness of our products, creating sales leads, nurturing prospective customers through the process of product discovery and evaluation, establishing and promoting our brand, and cultivating a

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community of successful and vocal customers. Based on our belief that the best method to sell subscriptions to our products is to provide customers with the opportunity to actively use and explore our products’ capabilities, one focus of our marketing team is to drive and encourage free trials and the successful conversion of free trials to paid subscriptions. We utilize both online and offline marketing initiatives, including search engine and email marketing, display and video advertising, blogs, corporate communications, whitepapers, case studies, user events, conferences, and webinars.

As of December 31, 2017, we had approximately 660 employees in our sales and marketing organizations. Our sales and marketing expenses were $220.7 million, $167.0 million, and $114.1 million for the years ended December 31, 2017, 2016, and 2015, respectively.

Product Support, Customer Success, and Professional Services

We strive to exemplify the great customer service that organizations of all sizes can provide with our products by offering multi-channel service from our product support team, a rich self-help knowledge base with detailed product guides, and active community forums for agents, managers, and developers.

We offer different levels of product support based upon the subscription plans purchased by our customers. Regardless of the plan purchased, our products provide a unified intuitive interface, connectivity to our self-help knowledge base and community forums, and step-by-step tutorials to help users learn, use, and deploy our products effectively.

We additionally offer a variety of customer success initiatives aimed to address customer needs with varying levels of complexity, from our small business customers to even our largest enterprise customers. These initiatives are designed to ensure that our customers are best equipped to meet their business goals and to realize the full value of the implementation of our products.

Along with our global partners, our professional services team assists our customers in implementing more complex deployments of our products. These services include mapping our products to new and existing business processes, data migration, and integration with existing systems. Service engagements are typically scoped on a time and materials or project milestone basis and billed separately from the subscription to our products.

Through our training platform, we offer courses to help our customers quickly learn how to effectively use our products as well as implement best practices. Courses are available online, in-person at events, and, as requested by certain customers, on-site. Our training sessions are typically targeted at specific levels of employee seniority and product experience, such as agent essentials or administrator expert, to more effectively tailor training to intended audiences.

Seasonality

Historically, we have experienced the highest demand for our products and services in our fourth quarter, which we believe is a result of industry buying patterns. For a more detailed discussion of the seasonality impacting our business, see the “Seasonality” discussion in the “Management’s Discussion and Analysis of Financial Condition and Results of Operations” section of this Annual Report on Form 10-K.

Competition

There are a number of established and emerging competitors in the broad market of customer engagement software. This market is fragmented, rapidly evolving, and highly competitive, with relatively low barriers to entry in some segments. We consider the principal competitive differentiators in our market to include:

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While we believe that we successfully compete with respect to these dynamics, given the large number, disparate sizes, and varying areas of focus of other companies with which we compete in the provision of customer engagement software, we may not always compare favorably with respect to some or all of the foregoing factors.

For small to medium-sized organizations, we often compete with general use computer applications and other tools that organizations have adapted for managing relationships with their customers, including shared accounts for email communication, phone banks for voice communication, and pen and paper, text editors, and spreadsheets for tracking and management. For larger organizations, we compete with custom software systems and large enterprise software vendors, including salesforce.com, Inc., Oracle Corporation, Microsoft Corporation, and ServiceNow, Inc. In addition, we compete with a number of other SaaS providers with focused applications competitive to one or more of our products, including applications developed by Freshworks, Inc. and desk.com (a salesforce.com service) that compete with Zendesk Support. Pricing pressures and increased competition generally could result in reduced sales, reduced margins, losses, or the failure of our family of products to achieve or maintain more widespread market acceptance, any of which could harm our business.

In order to maintain and improve our competitive position in the market, we remain focused in our development, operations, and sales and marketing efforts on the evolving customer service needs of all organizations.

Intellectual Property

We rely on a combination of patent, trade secret, copyright, and trademark laws, a variety of contractual arrangements, such as license agreements, assignment agreements, confidentiality and non-disclosure agreements, and confidentiality procedures and technical measures to gain rights to and protect the intellectual property used in our business.

We have developed a patent program, and a strategy to identify, apply for, and secure patents for innovative aspects of our platform and technology. We have two issued U.S. patents and ten U.S. patent applications pending. We intend to pursue additional patent protection to the extent we believe it would be beneficial and cost-effective.

We actively pursue registration of our trademarks, logos, service marks, and domain names in the United States and in other key jurisdictions. We are the registered holder of a variety of United States and international domain names that include the term Zendesk or certain variations. Our products and services utilize our “Zendesk” trademark as well as our logo and images.

We also rely on certain intellectual property rights that we license from third parties, including under certain open source licenses. Though such third-party technologies may not continue to be available to us on commercially reasonable terms, we believe that alternative technologies would be available to us.

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Our policy is to require employees and independent contractors to sign agreements assigning to us any inventions, trade secrets, works of authorship, developments, and other processes generated by them on our behalf and agreeing to protect our confidential information, and all of our key employees and contractors have done so. In addition, we generally enter into confidentiality agreements with our vendors and customers. We also control and monitor access to, and distribution of, our software, documentation, and other proprietary information.

Although we rely on intellectual property rights, including patents, trade secrets, copyrights, trademarks, a variety of contractual arrangements, and confidentiality procedures, we believe that factors such as the technical and creative skills of our personnel, development of new features and functionality, and frequent enhancements to our products are more fundamental to establishing and maintaining our technology leadership position.

Culture and Employees

As a company we are highly focused on our customers and their success. To support this focus, we highly value simplicity, agility, sincerity, as well as a sense of humor and humility often absent from enterprises that sell business software. These values guide our communication, work, and company culture and are a cornerstone of the team of employees that we have assembled and seek to develop. We are a global and diverse group of individuals that strive to balance work with play and that focus on big-scale thinking.

We believe strongly in our obligation to participate in and improve the communities in which we work and live. We do this by offering an active roster of corporate social responsibility engagements. In 2015, we launched the Zendesk Neighbor Foundation, a nonprofit organization dedicated to providing financial and strategic support to organizations that operate near our offices around the world. We have committed to provide a $1 donation to the Zendesk Neighbor Foundation for every new agent added during their first year of a new paid subscription plan on either Zendesk Support or Chat. In addition to our extensive volunteer efforts, we have continued to offer workforce development and training, financial support for critical community programs, and promotion of local arts and culture, with the communities in which our offices are located and our employees live and work.

As of December 31, 2017, we had approximately 2,060 employees, including approximately 940 employees located outside the United States. Although we have statutory employee representation obligations in certain countries, our U.S. employees are not represented by a labor union. We have not experienced any work stoppages, and we consider our relations with our employees to be good.

Regulatory Considerations

The legal environment of Internet-based businesses is evolving rapidly in the United States and elsewhere. The manner in which existing laws and regulations are applied in this environment, and how they will relate to our business in particular, both in the United States and internationally, is often unclear. For example, we sometimes cannot be certain which laws will be deemed applicable to us given the global nature of our business, including with respect to such topics as data privacy and security, pricing, credit card fraud, advertising, taxation, content regulation, and intellectual property ownership and infringement.

Our customers, and those with whom they communicate using our products, upload and store customer service and other data into our products and provide access to their data sources to our products, generally without any restrictions imposed by us. This presents legal challenges to our business and operations, such as rights of privacy related to the content loaded into our products. Both in the United States and internationally, we must monitor and comply with a host of legal concerns regarding the data stored and processed in our products as well as the operation of our business.

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We are subject to data privacy and security regulation by data protection authorities in countries throughout the world, by the U.S. federal government, and by the states in which we conduct our business. In recent years, there have been a number of well-publicized data breaches involving the improper use and disclosure of personal information of individuals. Many governing authorities have responded to these incidents by enacting laws requiring holders of personal information to maintain safeguards and to take certain actions in response to a data breach, such as providing prompt notification of the breach to affected individuals and public officials or amending existing laws to expand compliance obligations. In the European Union, U.S. companies must meet specified privacy and security standards, such as the Directive 95/46/EC, or the Directive, and, upon its effectiveness in May 2018, the European General Data Protection Regulation, or the GDPR, which govern the protection of individuals with regard to the processing of personally identifiable information, or PII, and on the free movement of such data established in the European Union to certain non-EU countries, such as the United States. Additionally, the data protection laws of each of the European Member countries require comprehensive information privacy and security protections for consumers with respect to PII collected about them. In February 2016, European Union and U.S. officials announced an agreement, the EU-U.S. Privacy Shield, or the Privacy Shield, as a means for legitimating the transfer of PII by U.S. companies doing business in Europe from the European Economic Area to the U.S. We have certified compliance with the Privacy Shield. In June 2017, we announced that we completed the EU approval process for our global Binding Corporate Rules (“BCRs”) as a data processor and controller. This significant regulatory approval validated our implementation of the highest possible standards for protecting PII globally, covering both the PII of our customers and employees. We have and expect to continue to engage in efforts to ensure that data transfers from the European Economic Area comply with the Directive, the GDPR, the Privacy Shield, our BCRs, and the data protection legislation of individual member states.

Geographic Information

For a description of our revenue and long-lived assets by geographic location, see Note 11 of the Notes to our Consolidated Financial Statements included elsewhere in this Annual Report on Form 10-K.

Additional Information

Our website is located at http://www.zendesk.com, and our investor relations website is located at http://investor.zendesk.com. Copies of our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K, and amendments to these reports filed or furnished pursuant to Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended, or the Exchange Act, are available, free of charge, on our investor relations website as soon as reasonably practicable after we file such material electronically with or furnish it to the Securities and Exchange Commission, or the SEC. The SEC also maintains a website that contains our SEC filings. The address of the site is http://www.sec.gov. Further, a copy of this Annual Report on Form 10-K is located at the SEC’s Public Reference Room at 100 F Street, NE, Washington, D.C. 20549. Information on the operation of the Public Reference Room can be obtained by calling the SEC at 1-800-SEC-0330.

We webcast our earnings calls and certain events we participate in or host with members of the investment community on our investor relations website. Additionally, we provide notifications of news or announcements regarding our financial performance, including SEC filings, investor events, press and earnings releases, and blogs as part of our investor relations website. We have used, and intend to continue to use, our investor relations website, as well as our Twitter account (@Zendesk), as means of disclosing material non-public information and for complying with our disclosure obligations under Regulation FD. Further corporate governance information, including our certificate of incorporation, bylaws, governance guidelines, board committee charters, and code of business conduct and ethics, is also available on our investor relations website under the heading “Corporate Governance.” The contents of our websites are not intended to be incorporated by reference into this Annual Report on Form 10-K or in any other report or document we file with the SEC, and any references to our websites are intended to be inactive textual references only.

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A description of the risks and uncertainties associated with our business is set forth below. You should carefully consider such risks and uncertainties, together with the other information contained in this report, and in our other public filings. If any of such risks and uncertainties actually occurs, our business, financial condition, or operating results could differ materially from the plans, projections, and other forward-looking statements included in the section titled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and elsewhere in this report and in our other public filings. In addition, if any of the following risks and uncertainties, or if any other risks and uncertainties, actually occurs, our business, financial condition, or operating results could be harmed substantially, which could cause the market price of our stock to decline, perhaps significantly.

Risks Related to Our Business

We derive, and expect to continue to derive, substantially all of our revenue and cash flows from Zendesk Support. If we fail to adapt this product to changing market dynamics and customer preferences or to achieve increased market acceptance of Support, our business, results of operations, financial condition, and growth prospects would be harmed.

We derive, and expect to continue to derive, substantially all of our revenue and cash flows from sales of subscriptions to Zendesk Support. As such, the market acceptance of this product is critical to our success. Demand for our products, including Support, is affected by a number of factors, many of which are beyond our control, such as continued market acceptance of our products by customers for existing and new use cases, the timing of development and release of new products, features, and functionality introduced by our competitors, technological change, and growth or contraction in our addressable market. We expect that an increasing focus on the customer experience and the growth of various communications channels will profoundly impact the market for customer support software and blur distinctions between traditionally separate systems for customer support, marketing automation, and customer relationship management, enabling new competitors to emerge. If we are unable to meet customer demands to improve relationships between organizations and their customers through products designed to address all these needs or otherwise achieve more widespread market acceptance of our products, including Support, our business, results of operations, financial condition, and growth prospects will be adversely affected.

We have a history of losses and we expect our revenue growth rate to decline. As our costs increase, we may not be able to generate sufficient revenue to achieve and sustain our profitability.

We have incurred net losses in each year since our inception, including net losses of $26.6 million and $24.5 million in the three months ended December 31, 2017 and 2016, respectively, and net losses of $110.6 million and $103.8 million for the fiscal years ended December 31, 2017 and 2016, respectively. We had an accumulated deficit of $430.6 million as of December 31, 2017. For the three months ended December 31, 2017 and 2016, our revenue was $123.4 million and $88.6 million, respectively, representing a 39% growth rate. For the fiscal years ended December 31, 2017 and 2016, our revenue was $430.5 million and $312.0 million, respectively, representing a 38% growth rate. We expect that our revenue growth rate will decline over time. We may not be able to generate sufficient revenue to achieve and sustain profitability as we also expect our costs to increase in future periods. We expect to continue to expend substantial financial and other resources on:

These investments may not result in increased revenue or growth of our business. If we fail to continue to grow our revenue, our operating results and business would be harmed.

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We have a limited operating history, which makes it difficult to predict future operating results.

We were incorporated and launched our first product in 2007. As a result of our limited operating history, our ability to accurately forecast our future operating results is limited and subject to a number of uncertainties, including our ability to plan for and model future growth. Our historical revenue growth has been inconsistent, and should not be considered indicative of our future performance. We have encountered and will continue to encounter risks and uncertainties frequently experienced by growing companies in rapidly changing industries, such as the risks and uncertainties described herein. If our assumptions regarding these risks and uncertainties, which we use to plan our business, are incorrect or change due to changes in our markets, or if we do not address these risks and uncertainties successfully, our operating and financial results could differ materially from our expectations, and our business could suffer.

The market in which we participate is intensely competitive, and if we do not compete effectively, our operating results could be harmed.

The market for customer service solutions is fragmented, rapidly evolving, and highly competitive, with relatively low barriers to entry. With respect to larger organizations and enterprises seeking to deploy a customer service software system, we have many competitors that are larger than us and which have greater name recognition, much longer operating histories, more established customer relationships, larger marketing budgets, and significantly greater resources than we do. Among the small to medium sized organizations that make up a large proportion of our customers, we often compete with general use computer applications and other tools, which these organizations use to provide support and which can be deployed for little or no cost. These include shared accounts for email communication, phone banks for voice communication, and pen and paper, text editors, and spreadsheets for tracking and management.

Our competitors may be able to respond more quickly and effectively than we can to new or changing opportunities, technologies, standards, or customer requirements. With the introduction of new technologies, the evolution of our products, and new market entrants, we expect competition to intensify in the future. Pricing pressures and increased competition generally could result in reduced sales, reduced margins, losses, or the failure of our products to achieve or maintain more widespread market acceptance, any of which could harm our business.

We face competition from in-house software systems, large integrated systems vendors, and smaller companies offering alternative SaaS applications. Our competitors vary in size and in the breadth and scope of the products and services they offer. For larger organizations, we compete with customer software systems and large enterprise software vendors such as salesforce.com, Inc., Oracle Corporation, Microsoft Corporation and ServiceNow, Inc., each of which can bundle competing products and services with other software offerings, or offer them at a low price as part of a larger sale. In addition, we compete with a number of other SaaS providers with focused applications competitive to one or more of our products, including applications developed by Freshworks, Inc. and desk.com (a salesforce.com service) that compete with Support. Further, other established SaaS providers not currently focused on the functionality that our products provide may expand their services to compete with us. Many of our current and potential competitors have established marketing relationships, access to larger customer bases, pre-existing customer relationships, and major distribution agreements with consultants, system integrators, and resellers. Additionally, some existing and potential customers, particularly large organizations, have elected, and may in the future elect, to develop their own internal customer support software system. Certain of our competitors have partnered with, or have acquired, and may in the future partner with or acquire, other competitors to offer services, leveraging their collective competitive positions, which makes, or would make, it more difficult for us to compete with them. For all of these reasons, we may not be able to compete successfully against our current and future competitors or retain existing customers, which would harm our business.

Our business depends substantially on our customers renewing their subscriptions, expanding the use of their subscriptions, and purchasing subscriptions for additional products from us. Any decline in our customer retention or expansion, or any failure by us to sell subscriptions to additional products to existing customers, would harm our future operating results.

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In order for us to maintain or improve our operating results, it is important that our customers renew their subscriptions when the initial contract term expires, and add additional authorized agents to their customer accounts. Even though the majority of our revenue is derived from subscriptions to our products that have terms longer than one month, a significant portion of the subscriptions to our products have monthly terms. Our customers have no obligation to renew their subscriptions, and our customers may not renew subscriptions with a similar contract period or with the same or a greater number of agents. Some of our customers have elected not to renew their agreements with us and we do not have enough history to accurately predict long-term customer retention. Additionally, our future success is also substantially dependent on our ability to expand our existing customers’ use of our products by expanding the number of products to which such customers subscribe. This may require increasingly sophisticated and costly sales efforts and may not result in additional sales.

Our customer retention and our ability to sell additional products to existing customers may be impacted by a number of factors, including our customers’ satisfaction with our products, our product support, our prices, the prices of competing software systems, mergers and acquisitions affecting our customer base, the effects of global economic conditions, or reductions in our customers’ spending levels. In addition, the rate at which our existing customers purchase subscriptions to additional products depends on a number of factors, including the perceived need for additional products to build better relationships between organizations and their customers. If our customers do not renew their subscriptions, renew on less favorable terms, fail to add more agents, or fail to purchase subscriptions to additional products, our revenue may decline, and we may not realize improved operating results from our customer base.

We may not be able to successfully introduce and market new products or integrate such new products into our infrastructure, which could negatively impact our future sales and results of operations.

Our ability to successfully introduce and market new products, as well as integrate such new products into a shared services infrastructure, is unproven. Because we have a limited operating history and the market for our products, including newly acquired or developed products, is rapidly evolving, it is difficult for us to predict our operating results, particularly with respect to any new products that we may introduce. Our business depends in part on our ability to identify future products that both complement our existing products and respond to our customers’ needs. Our customers also expect that new products will integrate with existing products that we currently offer. If we are not able to successfully introduce and commercialize new products that respond to customers’ needs, or to fully integrate such new products into our infrastructure, our business could be harmed. Furthermore, the success of our new products will depend on market demand, and there is a risk that new products and services we introduce will not deliver expected results, which could negatively impact our future sales and results of operations.

If we are not able to develop enhancements to our products or introduce new products and services that achieve market acceptance and that keep pace with technological developments, our business would be harmed.

Our ability to attract new customers and increase revenue from existing customers depends in large part on our ability to enhance and improve our products and to introduce new products and services. In order to grow our business, we must research and develop products and services that reflect the changing nature of customer service, and expand beyond customer service to other areas of improving relationships between organizations and their customers. In fiscal years ending 2017 and 2016, our research and development expenses were 27% and 29% of our revenue, respectively. If we do not spend our research and development budget efficiently or effectively on compelling innovation and technologies, our operating results may be harmed and we may not realize the expected benefits of our strategy.

The success of any enhancement to our products depends on several factors, including timely completion, adequate quality testing, and market acceptance. Any new product or service that we develop may not be introduced in a timely or cost-effective manner, may contain defects, or may not achieve the market acceptance necessary to generate sufficient revenue. If we are unable to successfully develop new products or services, enhance our existing products to meet customer requirements, or otherwise gain market acceptance, our business and operating results will be harmed.

Because our products are available over the Internet, we need to continuously modify and enhance them to keep pace with changes in Internet-related hardware, software, communications, and database technologies and standards. If we are unable to respond in a timely and cost-effective manner to these rapid technological developments and changes in standards, our products may become less marketable, less competitive, or obsolete, and our operating results will be harmed.

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We employ a pricing model that subjects us to various challenges that could make it difficult for us to derive sufficient value from our customers.

We generally charge our customers for their use of our products based on the number of users they enable as “agents” to provide customer service under their customer account, as well as the features and functionality enabled. The features and functionality we provide within our products enable our customers to promote customer self-service and otherwise efficiently and cost-effectively address product support requests without the need for substantial human interaction. As a result of these features, customer agent staffing requirements may be minimized and our revenue may be adversely impacted. Additionally, we generally require a separate subscription to enable the functionality of each of our products. We do not know whether our current or potential customers or the market in general will accept this pricing model going forward and, if it fails to gain acceptance, our business and results of operations could be harmed.

Our terms of service generally prohibit the sharing of user logins and passwords. These restrictions may be improperly circumvented or otherwise bypassed by certain users and, if they are, we may not be able to capture the full value of the use of our products. We license access and use of our products exclusively for our customers’ internal use. If customers improperly resell or otherwise make our products available to their customers, it may cannibalize our sales or commoditize our products in the market. Additionally, if a customer that has received a volume discount from us offers our products to its customers in violation of our terms of service, we may experience price erosion and be unable to capture sufficient value from the use of our products by those customers.

While our terms of service provide us the ability to enforce our terms, our customers may resist or refuse to allow us to audit their usage, in which case we may have to pursue legal recourse to enforce our rights. Any such enforcement action would require us to spend money, distract management, and potentially adversely affect our relationship with our customers.

We do not have the history with our subscription or pricing models that we need to accurately predict optimal pricing necessary to attract new customers and retain existing customers.

We have limited experience with respect to determining the optimal prices for our products and, as a result, we have in the past and expect in the future that we will need to change our pricing model from time to time. As the market for our products matures, or as new competitors introduce new products or services that compete with ours, we may be unable to attract new customers at the same price or based on the same pricing models as we have used historically. Pricing decisions may also impact the mix of adoption among our subscription plans and negatively impact our overall revenue. Moreover, larger organizations may demand substantial price concessions. As a result, in the future we may be required to reduce our prices or develop new pricing models, which could adversely affect our revenue, gross margin, profitability, financial position, and cash flow.

If we fail to effectively manage our growth and organizational change in a manner that preserves the key aspects of our culture, our business and operating results could be harmed.

We have experienced and may continue to experience rapid growth and organizational change, which has placed, and may continue to place, significant demands on our management, operational, and financial resources. For example, our headcount has grown from approximately 1,630 employees as of December 31, 2016 to approximately 2,060 employees as of December 31, 2017. In addition, we have established subsidiaries in Denmark, the United Kingdom, Australia, Ireland, Japan, the Philippines, Brazil, Germany, India, and Mexico since our inception in 2007, and, as a result of acquisitions, we also have

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subsidiaries in Singapore and France. We may continue to expand our international operations into other countries in the future. We have also experienced significant growth in the number of customers, end users, transactions, and data that our products support. Finally, our organizational structure is becoming more complex and we may need to scale and adapt our operational, financial, and management controls, as well as our reporting systems and procedures, to manage this complexity. We will require significant capital expenditures and the allocation of valuable management resources to grow and change in these areas without undermining our corporate culture of rapid innovation, simplicity in design, and attention to customer satisfaction that has been critical to our growth so far. If we fail to manage our anticipated growth and change in a manner that preserves the key aspects of our culture, the quality of our products and services may suffer, which could negatively affect our brand and reputation and harm our ability to retain and attract customers.

If the market for SaaS business software applications develops more slowly than we expect or declines, our business would be adversely affected.

The market for SaaS business software applications is less mature than the market for on-premise business software applications, and the adoption rate of SaaS business software applications may be slower among subscribers in industries with heightened data security interests or business practices requiring highly customizable application software. Our success will depend to a substantial extent on the widespread adoption of SaaS business applications in general, and of SaaS customer service applications in particular. Many organizations have invested substantial personnel and financial resources to integrate traditional on-premise business software applications into their businesses, and therefore may be reluctant or unwilling to migrate to SaaS applications. It is difficult to predict customer adoption rates and demand for our products, the future growth rate and size of the SaaS business applications market, or the entry of competitive applications. The expansion of the SaaS business applications market depends on a number of factors, including the cost, performance, and perceived value associated with SaaS, as well as the ability of SaaS providers to address data security and privacy concerns. Additionally, government agencies have adopted, or may adopt, laws and regulations regarding the collection, use, and transfer of personal information obtained from consumers and other individuals, or may seek to access information on our platform, either of which may reduce the overall demand for our products. If we or other SaaS providers experience data security incidents, loss of customer data, disruptions in delivery, or other problems, the market for SaaS business applications, including our products, may be negatively affected. If SaaS business applications do not continue to achieve market acceptance, if there is a reduction in demand for SaaS business applications caused by a lack of customer acceptance, or if there are technological challenges, weakening economic conditions, data security or privacy concerns, governmental regulation, competing technologies and products, or decreases in information technology spending, it would result in decreased revenue and our business would be adversely affected.

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If our network or computer systems are breached or unauthorized access to customer data is otherwise obtained, our products may be perceived as insecure, we may lose existing customers or fail to attract new customers, and we may incur significant liabilities.

Use of our products involves the storage, transmission, and processing of our customers’ proprietary data, including personal or identifying information regarding their customers or employees. Unauthorized access to or security breaches of our products could result in the loss of data, loss of intellectual property or trade secrets, loss of business, severe reputational damage adversely affecting customer or investor confidence, regulatory investigations and orders, litigation, or indemnity obligations. Furthermore, if our network or computer systems are breached or unauthorized access to customer data is otherwise obtained, we may be held responsible for damages for contract breach, penalties for violation of applicable laws, regulations, or contractual obligations, and significant costs for remediation that may include liability for stolen assets or information and repair of system damage that may have been caused, incentives offered to customers or other business partners in an effort to maintain business relationships after a breach, and other liabilities. Notifications related to a security breach regarding or pertaining to any of such service providers could impact our reputation, harm customer confidence, hurt our sales and expansion into new markets, or cause us to lose existing customers. We have incurred, and expect to continue to incur, significant expenses to prevent, investigate, and remediate security breaches and vulnerabilities, including deploying additional personnel and protection technologies, training employees, and engaging third-party experts and consultants. Our errors and omissions insurance coverage covering certain security and privacy damages and claim expenses may not be sufficient to compensate for all liability.

We have previously experienced significant breaches and identified significant vulnerabilities of our security measures and the security measures deployed by third-party vendors upon which we rely, and our products are at risk for future breaches as a result of third-party action, employee, vendor, or contractor error, malfeasance, or other factors.

New products and services, including newly acquired products and services, may rely on systems, networks, personnel, equipment, and vendors that may initially be different from those utilized in connection with our existing products and may not have been subject to the same security reviews and assessments as those used to provide our existing products. Any failure to complete these security reviews and assessments and to implement improvements to the security measures deployed to protect our new products in a timely manner could increase our risk of a security breach with respect to these products, which would harm our reputation and our business as a whole.

Because the techniques used and vulnerabilities exploited to obtain unauthorized access to or to sabotage systems change frequently and generally are not identified until they are launched against a target, we may be unable to anticipate these techniques or vulnerabilities or to implement adequate preventative measures. We may also experience security breaches that may remain undetected for an extended period.

Because data security is a critical competitive factor in our industry, we make numerous statements in our privacy policies, terms of service and data processing agreements, through our certifications to privacy standards, and in our marketing materials, providing assurances about the security of our products, including detailed descriptions of security measures we employ. Should any of these statements be untrue or become untrue, even due to circumstances beyond our reasonable control, we may face claims of misrepresentation or deceptiveness by the U.S. Federal Trade Commission, state and foreign regulators, and private litigants.

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Interruptions or performance problems associated with our technology and infrastructure may adversely affect our business and operating results.

Our continued growth depends in part on the ability of our existing and potential customers to access our products at any time and within an acceptable amount of time. Our products are proprietary, and we rely on the expertise of members of our engineering, operations, and software development teams for their continued performance. We have experienced, and may in the future experience, disruptions, outages, and other performance problems due to a variety of factors, including infrastructure changes, introductions of new functionality, human or software errors, capacity constraints due to an overwhelming number of users simultaneously accessing our products, distributed denial of service attacks, or other security related incidents. In some instances, we may not be able to identify the cause or causes of these performance problems within an acceptable period of time. It may become increasingly difficult to maintain and improve our performance, especially during peak usage times and as our products become more complex and our user traffic increases. If any of our products are unavailable or if our users are unable to access our products within a reasonable amount of time or at all, our business would be negatively affected. In addition, a significant portion of our infrastructure does not currently support the mirroring of data. Therefore, in the event of any of the factors described above, or certain other failures of our infrastructure, customer data may be permanently lost. Moreover, some of our customer agreements and certain subscription plans include performance guarantees and service level standards that obligate us to provide credits or termination rights in the event of a significant disruption in our services. To the extent that we do not effectively address capacity constraints, upgrade our systems as needed, and continually develop our technology and network architecture to accommodate actual and anticipated changes in technology, our business and operating results may be adversely affected.

Real or perceived errors, failures, or bugs in our products could adversely affect our operating results and growth prospects.

Because our products are complex, undetected errors, failures, vulnerabilities, or bugs may occur, especially when updates are deployed. Our products are often used in connection with large-scale computing environments with different operating systems, system management software, equipment, and networking configurations, which may cause errors or failures of our products or other aspects of the computing environment into which they are deployed. In addition, deployment of our products into complicated, large-scale computing environments may expose undetected errors, failures, vulnerabilities, or bugs in our products. We have discovered, and expect to continue to discover, software errors, failures, vulnerabilities, and bugs in our products, some of which have or may only be discovered and remediated after deployment to customers. Real or perceived errors, failures, vulnerabilities, or bugs in our products could result in negative publicity, loss of or delay in market acceptance of our products, loss of competitive position, or claims by customers for losses sustained by them. In such an event, we may be required, or may choose, for customer relations or other reasons, to expend additional resources in order to help correct the problem.

Incorrect or improper implementation or use of our products could result in customer dissatisfaction and negatively affect our business, results of operations, financial condition, and growth prospects.

Our products are deployed in a wide variety of technology environments and into a broad range of complex workflows. Increasingly, our products have been, and will continue to be, integrated into large-scale, complex technology environments and specialized use cases, and we believe our future success will depend on our ability to increase use of our products in such deployments. We often assist our customers in implementing our products, but many customers attempt to implement deployments, including complex deployments, themselves. If we or our customers are unable to implement our products successfully, or are unable to do so in a timely manner, customer perceptions of our products and of our company may be impaired, our reputation and brand may suffer, and customers may choose not to renew or expand the use of our products.

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Our customers and third-party partners may need training in the proper use of our products to maximize their potential. If our products are not implemented or used correctly or as intended, inadequate performance may result. Because our customers rely on our products to manage a wide range of operations and to drive a number of their internal processes, the incorrect or improper implementation or use of our products, our failure to train customers on how to efficiently and effectively use our products, or our failure to provide adequate product support to our customers, may result in negative publicity or legal claims against us. Also, as we continue to expand our customer base, any failure by us to properly provide these services will likely result in lost opportunities for additional subscriptions to our products.

Any failure to offer high-quality product support or customer success initiatives may adversely affect our relationships with our customers and our financial results.

In deploying and using our products, our customers depend on our product support team and customer success organization to resolve complex technical and operational issues. We may be unable to respond quickly enough to accommodate short-term increases in customer demand for product support. We also may be unable to modify the nature, scope, and delivery of our product support to compete with changes in product support services provided by our competitors. Increased customer demand for product support, without corresponding revenue, could increase costs and adversely affect our operating results. Additionally, we may be unable to develop our customer success organization to continue to support the increasing level of complexity that larger enterprise customers require while maintaining the same level of engagement across all customers.

Our sales are highly dependent on our business reputation and on positive recommendations from our existing customers. Any failure to maintain high-quality product support, or a market perception that we do not maintain high-quality product support, or maintain a high-complexity customer success organization, could adversely affect our reputation, our ability to sell our products to existing and prospective customers, and our business, operating results, and financial position.

We depend on our executive officers and other key employees and the loss of one or more of these employees or an inability to attract and retain highly skilled employees could adversely affect our business.

Our success depends largely upon the continued services of our executive officers and other key employees. We rely on our leadership team and on individual contributors in the areas of research and development, operations, security, sales, marketing, support, and general and administrative functions. From time to time, there may be changes in our executive management team resulting from the hiring or departure of executives, which could disrupt our business.

We do not have employment agreements with our executive officers or other key personnel that require them to continue to work for us for any specified period of time and, therefore, they could terminate their employment with us at any time. The loss of one or more of our executive officers, especially our Chief Executive Officer, or other key employees could have an adverse effect on our business.

In addition, to execute on our growth plan, we must attract and retain highly qualified personnel. Competition for these personnel in the San Francisco Bay Area, where our headquarters is located, and in other locations where we maintain offices, is intense, especially for engineers experienced in designing and developing software and SaaS applications and experienced sales professionals. We have, from time to time, experienced, and we expect to continue to experience, difficulty in hiring and retaining employees with appropriate qualifications. For example, certain domestic immigration laws restrict or limit our ability to recruit internationally. Any changes to U.S. immigration policies that restrain the flow of technical and professional talent may inhibit our ability to recruit and retain highly qualified employees. Additionally, many of the companies with which we compete for experienced personnel have greater resources than we have. If we hire employees from competitors or other companies, their former employers may attempt to assert that these employees or we have breached their legal obligations, resulting in a diversion of our time and resources. In addition, job candidates and existing employees often consider the value of the equity awards they receive in connection with their employment. If the perceived or actual value of our equity awards declines, it may adversely affect our ability to recruit and retain highly skilled employees. If we fail to attract new personnel, or fail to retain and motivate our current personnel, our business and future growth prospects could be adversely affected.

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We are highly dependent upon free trials of our products and other inbound lead generation strategies to drive our sales and revenue. If these strategies fail to continue to generate sales opportunities or do not convert into paying customers, our business and results of operations would be harmed.

We are dependent upon our marketing strategy of offering free trials of our products and other inbound lead generation strategies to generate sales opportunities. These strategies may not be successful in continuing to generate sufficient sales opportunities necessary to increase our revenue. Many early users never convert from the trial version of a product to a paid version of such product. Further, we often depend on individuals within an organization who initiate the trial versions of our products being able to convince decision makers within their organization to convert to a paid version. Many of these organizations have complex and multi-layered purchasing requirements. To the extent that these users do not become, or are unable to convince others to become, paying customers, we will not realize the intended benefits of this marketing strategy and our ability to grow our revenue will be adversely affected.

We face a number of risks in our strategy to increasingly target larger organizations for sales of our products and, if we do not manage these efforts effectively, our business and results of operations could be adversely affected.

As we target more of our sales efforts to larger organizations, we expect to incur higher costs and longer sales cycles and we may be less effective at predicting when we will complete these sales. In this market segment, the decision to subscribe to one or more of our products may require the approval of a greater number of technical personnel and management levels within a potential customer’s organization than we have historically encountered, and if so, these types of sales would require us to invest more time educating these potential customers on the benefits of our products. In addition, larger organizations may demand more features and integration services. We have limited experience in developing and managing sales channels and distribution arrangements for larger organizations. As a result of these factors, these sales opportunities may require us to devote greater research and development, sales, product support, and professional services resources to individual customers, resulting in increased costs and reduced profitability, and would likely lengthen our typical sales cycle, which could strain our resources. Moreover, these transactions may require us to delay recognizing the associated revenue we derive from these customers until any technical or implementation requirements have been met, and larger customers may demand discounts to the subscription prices they pay for our products. Furthermore, because we have limited experience selling to larger organizations, our investment in marketing our products to these potential customers may not be successful, which could harm our results of operations and our overall ability to grow our customer base. Following sales to larger organizations, we may have fewer opportunities to expand usage of our products or to sell additional functionality, and we may experience increased subscription terminations as compared to our experience with smaller organizations, any of which could harm our results of operations.

Failure to effectively expand our sales capabilities could harm our ability to increase our customer base and achieve broader market acceptance of our products.

Increasing our customer base and achieving broader market acceptance of our products will depend, to a significant extent, on our ability to effectively expand our sales and marketing operations and activities. We are substantially dependent on our direct sales force to obtain certain of our new customers, including larger organizations. We plan to continue to expand our direct sales force both domestically and internationally to increase our sales capacity. During the twelve months ended December 31, 2017, our sales and marketing organization increased by approximately 180 employees to approximately 660 employees. There is significant competition for experienced sales and marketing professionals with the skills and technical knowledge that we require. Our ability to achieve significant revenue growth in the future will depend, in part, on our success in recruiting, training, and retaining a sufficient number of experienced sales and marketing professionals. New hires require significant training and time before they achieve full productivity, particularly in new sales segments and territories. Our recent hires and planned hires may not become as productive as we anticipate as quickly as we expect, and we may be unable to hire or retain sufficient numbers of qualified individuals in the future in the markets where we do business. We cannot predict whether, or to what extent, our sales will increase as we expand our sales and marketing functions or how long it will take for new personnel to become productive. Our business will be harmed if our sales and marketing efforts do not generate a significant increase in revenue.

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Our financial results may fluctuate due to increasing variability in our sales cycles.

We plan our expenses based on certain assumptions about the length and variability of our sales cycle. These assumptions are based upon historical trends for sales cycles and conversion rates associated with our existing customers, many of whom to date have been small to medium-sized organizations that make purchasing decisions with limited interaction with our sales or other personnel. As we continue to become more dependent on sales to larger organizations, we expect our sales cycles to lengthen and become less predictable. This may adversely affect our financial results. Factors that may influence the length and variability of our sales cycle include:

An increasing dependence on sales to larger organizations may increase the variability of our financial results. If we are unable to close one or more expected significant transactions with these customers in a particular period, or if an expected transaction is delayed until a subsequent period, our operating results for that period, and for any future periods in which revenue from such transaction would otherwise have been recognized, may be adversely affected.

Our quarterly results may fluctuate for various other reasons, and if we fail to meet the expectations of analysts or investors, our stock price and the value of an investment in our common stock could decline substantially.

Our quarterly financial results may fluctuate as a result of a variety of other factors, many of which are outside of our control. If our quarterly financial results fall below the expectations of investors or any securities analysts who follow our stock, the price of our common stock could decline substantially. Some of the important factors that may cause our revenue, operating results, and cash flows to fluctuate from quarter to quarter include:

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Many of these factors are outside of our control, and the occurrence of one or more of them might cause our revenue, operating results, and cash flows to vary widely. As such, we believe that quarter-to-quarter comparisons of our revenue, operating results, and cash flows may not be meaningful and should not be relied upon as an indication of future performance.

Unfavorable conditions in our industry or the global economy or reductions in information technology spending could limit our ability to grow our business and negatively affect our operating results.

Our operating results may vary based on the impact of changes in our industry or the global economy on us or our customers. The revenue growth and potential profitability of our business depend on demand for business software applications and services generally and for customer service systems in particular. In addition, our revenue is dependent on the number of users of our products, which in turn is influenced by the employment and hiring patterns of our customers. To the extent that weak economic conditions cause our customers and prospective customers to freeze or reduce their hiring for personnel providing service and support, demand for our products may be negatively affected. Historically, during economic downturns there have been reductions in spending on information technology and customer service systems as well as pressure for extended billing terms and other financial concessions. If economic conditions deteriorate, our customers and prospective customers may elect to decrease their information technology and customer service budgets, which would limit our ability to grow our business and negatively affect our operating results.

If we are unable to develop and maintain successful relationships with channel partners, our business, operating results, and financial condition could be adversely affected.

To date, we have been primarily dependent on our direct sales force to sell subscriptions to our products. Although we have developed certain channel partners, such as referral partners, resellers, and integration partners, these channels have resulted in limited revenue to date. We believe identifying, developing, and maintaining strategic relationships with additional channel partners are important to driving revenue growth for our company and will continue to dedicate resources to those efforts. Our agreements with our existing channel partners are non-exclusive, meaning our channel partners may offer customers the products of several different companies, including products that compete with ours. They may also cease marketing our products with limited or no notice and with little or no penalty. We expect that any additional channel partners we identify and develop will be similarly non-exclusive and not bound by any requirement to continue to market our products. If we fail to identify additional channel partners, in a timely and cost-effective manner, or at all, or are unable to assist our current and future channel partners in independently selling and deploying our products, our business, results of operations, and financial condition could be adversely affected. Additionally, customer retention and expansion attributable to customers acquired through our channel partners may differ significantly from customers acquired through our direct sales efforts. If our channel partners do not effectively market and sell our products, or fail to meet the needs of our customers, our reputation and ability to grow our business may also be adversely affected.

Sales by channel partners are more likely than direct sales to involve collectibility concerns. In particular sales by our channel partners into developing markets, and accordingly, variations in the mix between revenue attributable to sales by channel partners and revenue attributable to direct sales, may result in fluctuations in our operating results.

If we are not able to maintain and enhance our brand, our business, operating results, and financial condition may be adversely affected.

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We believe that maintaining and enhancing our reputation as a differentiated and category-defining company in customer service is critical to our relationships with our existing customers and to our ability to attract new customers. The successful promotion of our brand attributes will depend on a number of factors, including our marketing efforts, our ability to continue to develop high-quality software, and our ability to successfully differentiate our products from competitive products and services. We are highly dependent upon “consumer” tactics, including an emphasis on simplicity and a sense of humor in our advertising, to build our brand and develop brand loyalty. Additionally, we will continue to spend significant energy to develop branding to retain and increase brand recognition with our customers who are larger enterprises. We do not have sufficient history to know if any of our brand promotion activities will ultimately be successful or yield increased revenue relative to traditional enterprise software marketing strategies. In addition, independent industry analysts often provide reviews of our products, as well as products and services offered by our competitors, and perception of our products in the marketplace may be significantly influenced by these reviews. If these reviews are negative, or less positive as compared to those of our competitors’ products and services, our brand may be adversely affected. It may also be difficult to maintain and enhance our brand, specifically following the launch of our updated corporate brand, in connection with sales through channel or strategic partners.

The promotion of our brand requires us to make substantial expenditures, and we anticipate that these expenditures will continue to increase, as our market becomes more competitive, as we expand into new markets, and as more sales are generated through our channel partners. To the extent that these activities yield increased revenue, this revenue may not offset the increased expenses we incur. If we do not successfully maintain and enhance our brand, our business may not grow, we may have reduced pricing power relative to competitors, and we could lose customers or fail to attract potential customers, all of which would adversely affect our business, results of operations, and financial condition.

Our international sales and operations subject us to additional risks that can adversely affect our business, operating results, and financial condition.

In the three months and fiscal years ended December 31, 2017 and 2016, we derived 47% and 46% of our revenue from customers located outside of the United States, respectively. We are continuing to expand our international operations as part of our growth strategy. We currently have sales personnel and sales and product support operations in certain countries across North America, Europe, Australia, Asia, and South America. To date a very limited portion of our sales has been driven by resellers or other channel partners. We believe our ability to convince new customers to subscribe to our products or to convince existing customers to renew or expand their use of our products is directly correlated to the level of engagement we obtain with the customer. To the extent we are unable to effectively engage with non-U.S. customers due to our limited sales force capacity and limited channel partners, we may be unable to effectively grow in international markets.

Our international operations subject us to a variety of additional risks and challenges, including:

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Any of these risks could adversely affect our international operations, reduce our international revenue, or increase our operating costs, adversely affecting our business, operating results, financial condition, and growth prospects.

Compliance with laws and regulations applicable to our international operations substantially increases our cost of doing business in foreign jurisdictions. We may be unable to keep current with new or revised government requirements as they change from time to time. Failure to comply with these regulations could have adverse effects on our business. Additionally, in many foreign countries it is common for others to engage in business practices that are prohibited by our internal policies and procedures or U.S. or other regulations applicable to us. Although we have implemented policies and procedures designed to ensure compliance with these laws and policies, there can be no assurance that all of our employees, contractors, partners, and agents will comply with these laws and policies. Violations of laws or key control policies by our employees, contractors, partners, or agents could result in delays in revenue recognition, financial reporting misstatements, enforcement actions, disgorgement of profits, fines, civil and criminal penalties, damages, injunctions, other collateral consequences, or the prohibition of the importation or exportation of our products and services and could adversely affect our business and results of operations.

We are subject to governmental export and import controls that could impair our ability to compete in international markets or subject us to liability if we violate the controls.

We are subject to U.S. export controls, and we incorporate encryption technology into our products that is enabled through mobile applications and other software we may be deemed to export. These encryption products and the underlying technology may be exported outside of the U.S. only with the required export authorizations, including by license, a license exception, or other appropriate government authorizations, including the filing of an encryption registration. We previously deployed mobile applications prior to obtaining the required export authorizations. Accordingly, we have not fully complied with applicable encryption controls in U.S. export administration regulations.

Furthermore, U.S. export controls laws and economic sanctions prohibit the shipment of certain products and services to countries, governments, territories, and persons targeted by U.S. sanctions. While we are currently taking precautions to prevent our products from being enabled by persons targeted by U.S. sanctions, including IP blocking and periodic customer screening against U.S. government lists of prohibited persons, such measures may be circumvented. Given the technical limitations in developing measures that will prevent access to internet based services from particular geographies or by particular individuals, we have previously identified and expect we will continue to identify customer accounts for our products that we suspect originate from countries which are subject to U.S. embargoes.

We are aware that trials of and subscriptions to our products have been initiated by persons and organizations in countries that are the subject of U.S. embargoes. Our provision of services in these instances was likely in violation of U.S.

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export controls and sanctions laws. We have terminated the accounts of such organizations as we have become aware of them, implemented certain measures designed to prevent future unauthorized access by such persons and organizations, and filed voluntary self disclosures with the U.S. Department of Commerce’s Bureau of Industry and Security, or BIS, and the U.S. Department of Treasury’s Office of Foreign Assets Control, or OFAC, concerning prior potential violations. With respect to these matters, each of BIS and OFAC completed its investigations, and no monetary penalties or other sanctions were imposed.

If we are found to be in violation of U.S. sanctions or export controls laws, it could result in fines or penalties for us and for individuals, including civil penalties of approximately $300,000 or twice the value of the transaction, whichever is greater, per violation, and in the event of conviction for a criminal violation, fines of up to $1 million and possible incarceration for responsible employees and managers for willful and knowing violations. Each instance in which we provide services through our products or in which unlicensed encryption functionality software is downloaded may constitute a separate violation of these laws.

If our channel partners fail to obtain appropriate import, export, or re-export licenses or permits, we may also be adversely affected, through reputational harm as well as other negative consequences, including government investigations and penalties. We presently incorporate sanctions compliance requirements in our channel partner agreements for our products. Complying with export controls and sanctions regulations for a particular sale may be time-consuming and may result in the delay or loss of sales opportunities. Failure to comply with exports control and sanctions regulations for a particular sale may expose us to government investigations and penalties, which could have an adverse effect on our business, operating results, and financial condition.

In addition, various countries regulate the import of certain encryption technology, including import permitting and licensing requirements, and have enacted laws that could limit our ability to offer or distribute our products or could limit our customers’ ability to implement our products in those countries. Changes in our products or future changes in export and import regulations may create delays in the introduction of our products in international markets or prevent our customers with international operations from deploying our products globally. Any change in export or import regulations, economic sanctions, or related legislation, or change in the countries, governments, persons, or technologies targeted by such regulations, could result in decreased use of our products by, or in our decreased ability to export or sell our products to, existing or potential customers with international operations. Any decreased use of our products or limitation on our ability to export or sell our products would likely adversely affect our business operations and financial results.

We recognize revenue over the term of our customer contracts. Consequently, downturns or upturns in new sales may not be immediately reflected in our operating results and may be difficult to discern.

We generally recognize subscription revenue from customers ratably over the terms of their contracts and a majority of our revenue is derived from subscriptions that have terms longer than one month. As a result, a portion of the revenue we report in each quarter is derived from the recognition of deferred revenue relating to subscriptions entered into during previous quarters. Consequently, a decline in new or renewed subscriptions with terms that are longer than one month in any single quarter may have a small impact on our revenue results for that quarter. However, such a decline will negatively affect our revenue in future quarters. Accordingly, the effect of significant downturns in sales and market acceptance of our products, and potential changes in our pricing policies or rate of expansion or retention, may not be fully reflected in our results of operations until future periods. We may also be unable to reduce our cost structure in line with a significant deterioration in sales. In addition, because we believe a substantial percentage of subscriptions to our products are shorter than many comparable SaaS companies and because we have many variations of billing cycles, our deferred revenue may be a less meaningful indicator of our future financial results as compared to other SaaS companies. A significant majority of our costs are expensed as incurred, while revenue is recognized over the life of the agreement with the applicable customer. As a result, increased growth in the number of our customers could continue to result in our recognition of more costs than revenue in the earlier periods of the terms of our agreements. Our subscription model also makes it difficult for us to rapidly increase our revenue through additional sales in any period, as revenue from new customers must be recognized over the applicable subscription term.

Certain of our operating results and financial metrics may be difficult to predict as a result of seasonality.

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We have experienced, and expect to continue to experience in the future, seasonality in our business, and our operating results and financial condition may be affected by such trends in the future. We generally experience seasonal fluctuations in demand for our products and services, and believe that our quarterly sales are affected by industry buying patterns. For example, we typically have customers who add flexible agents when they need more capacity during busy periods, especially in the fourth quarter, and then subsequently scale back in the first quarter of the following year. We believe that the seasonal trends that we have experienced in the past may continue for the foreseeable future, particularly as we expand our sales to larger enterprises. Additionally, since a large percentage of our subscriptions are monthly, customers are able to increase and decrease the number of authorized agents for whom they require a subscription quickly and easily, thereby potentially increasing the impact of seasonality on our revenue. Seasonality within our business may be reflected to a much lesser extent, and sometimes may not be immediately apparent, in our revenue, due to the fact that we recognize subscription revenue over the term of our agreement. To the extent we experience this seasonality, it may cause fluctuations in our operating results and financial metrics, and make forecasting our future operating results and financial metrics difficult. Additionally, we do not have sufficient experience in selling certain of our products to determine if demand for these services are or will be subject to material seasonality.

Our ongoing and planned expenditures on third-party managed hosting services, investments in self-managed colocation data centers, and expenditures on transitioning our services and customers fully to third-party managed hosting services, are expensive and complex, have resulted, and will result, in a negative impact on our cash flows, and may negatively impact our financial results.

We have made and will continue to make substantial expenditures for third-party managed hosting services and investments in our self-managed colocation data centers to support our growth and provide enhanced levels of service to our customers. We recently decreased the amount of capital expenditures on hosting equipment for use in our self-managed colocation data centers as we transition to greater dependence on third-party managed hosting services, but expect to continue to incur significant expense to operate and maintain our self-managed colocation data centers. We have employed a hybrid hosting model in which we utilize managed hosting services, where a third party manages most aspects of our hosting operations, and self-managed colocation data centers, where we have more direct control over the hosting infrastructure and its operation. This has and may continue to have a negative impact on our cash flows and gross profit. If costs associated with third-party managed hosting services utilized to support our growth are greater than expected or if we are required to make larger investments in our self-managed colocation data centers than we anticipated, the negative impact on our operating results would likely exceed our initial expectations. Furthermore, if we determine to no longer utilize our self-managed colocation data centers, we may be forced to accelerate expense recognition as a result of the shorter estimated life of such assets.

We plan to continue to invest significant resources in connection with transitioning our customers and services infrastructure to third-party managed hosting services and may encounter obstacles in completing the transition. Given that we will increasingly become more reliant on third-party managed hosting services, any significant disruption of or interference in our use of such services will negatively impact our operations and customer satisfaction. In addition, third-party managed hosting services may take actions beyond our control that could seriously harm our business, including:

Our business and growth depend in part on the success of our strategic relationships with third parties, including technology partners, channel partners, and professional services partners.

We depend on, and anticipate that we will continue to depend on, various third-party relationships in order to sustain and grow our business. We are highly dependent upon third-party technology partners for certain critical features and

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functionality of our platform. For example, the features available on Zendesk Talk are highly dependent on our technology integration with Twilio, Inc. Failure of this or any other technology provider to maintain, support, or secure its technology platforms in general, and our integrations in particular, or errors or defects in its technology, could materially and adversely impact our relationship with our customers, damage our reputation and brand, and harm our business and operating results. Any loss of the right to use any of this hardware or software could result in delays or difficulties in our ability to provide our products until equivalent technology is either developed by us or, if available, identified, obtained, and integrated.

For deployments of our products into complex technology environments and workflows, we are highly dependent on third-party implementation consultants to provide professional services to our customers. The failure of these third-party consultants to perform their services adequately may disrupt or damage the relationship between us and our customers, damage our brand, and harm our business.

Identifying, negotiating, and documenting relationships with strategic third parties such as technology partners and implementation providers require significant time and resources. In addition, integrating third-party technology is complex, costly, and time-consuming. Our agreements with technology partners and implementation providers are typically limited in duration, non-exclusive, and do not prohibit them from working with our competitors or from offering competing services. Our competitors may be effective in providing incentives to third parties to favor their products or services or to prevent or reduce subscriptions to our products.

If we are unsuccessful in establishing or maintaining our relationships with these strategic third parties, our ability to compete in the marketplace or to grow our revenue could be impaired and our operating results would suffer. Even if we are successful, we cannot assure you that these relationships will result in improved operating results.

If we fail to integrate our products with a variety of operating systems, software applications, and hardware that are developed by others, our products may become less marketable, less competitive, or obsolete, and our operating results would be harmed.

Our products must integrate with a variety of network, hardware, and software platforms, and we need to continuously modify and enhance our products to adapt to changes in cloud-enabled hardware, software, networking, browser, and database technologies. In particular, we have developed our products to be able to easily integrate with third-party SaaS applications, including the applications of software providers that compete with us, through the interaction of application platform interfaces, or APIs. To date, we have not typically relied on a long-term written contract to govern our relationship with these providers. Instead, we are typically subject to the standard terms and conditions for application developers of such providers, which govern the distribution, operation, and fees of such software systems, and which are subject to change by such providers from time to time. To the extent that we do not have long-term written contracts to govern our relationship with these providers, we rely on the fact that the providers of such software systems continue to allow us access to their APIs to enable these customer integrations. Our business may be harmed if any provider of such software systems:

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We believe a significant component of our value proposition to customers is the ability to optimize and configure our products to communicate with these third-party SaaS applications through our respective APIs. If we are not permitted or able to integrate with these and other third-party SaaS applications in the future, demand for our products could be adversely impacted and business and operating results would be harmed. In addition, an increasing number of individuals within organizations are utilizing mobile devices to access the Internet and corporate resources and to conduct business. We have designed mobile applications to provide access to our products through these devices. If we cannot provide effective functionality through these mobile applications as required by organizations and individuals that widely use mobile devices, we may experience difficulty attracting and retaining customers. Failure of our products to operate effectively with future infrastructure platforms and technologies could also reduce the demand for our products, resulting in customer dissatisfaction and harm to our business. If we are unable to respond to changes in a cost-effective manner, our products may become less marketable, less competitive, or obsolete and our operating results may be negatively impacted.

We may acquire or invest in companies, which may divert our management’s attention and result in additional dilution to our stockholders. We may be unable to integrate acquired businesses and technologies successfully or achieve the expected benefits of such acquisitions.

We may evaluate and consider potential strategic transactions, including acquisitions of, or investments in, businesses, technologies, services, products, and other assets in the future. We also may enter into relationships with other businesses to expand our products and services, which could involve preferred or exclusive licenses, additional channels of distribution, discount pricing, or investments in other companies.

Any acquisition, investment, or business relationship may result in unforeseen operating difficulties and expenditures. In particular, we may encounter difficulties assimilating or integrating the businesses, technologies, products, personnel, or operations of the acquired companies, particularly if the key personnel of the acquired company choose not to work for us, their software is not easily adapted to work with our products, or we have difficulty retaining the customers of any acquired business due to changes in ownership, management, or otherwise. Acquisitions may also disrupt our business, divert our resources, and require significant management attention that would otherwise be available for development of our existing business. Moreover, the anticipated benefits of any acquisition, investment, or business relationship may not be realized or we may be exposed to unknown risks or liabilities.

Negotiating these transactions can be time-consuming, difficult, and expensive, and our ability to complete these transactions may often be subject to approvals that are beyond our control. Consequently, these transactions, even if announced, may not be completed. For one or more of these transactions, we may:

Because our products can be used to collect and store personal information, domestic and international privacy and data security concerns could result in additional costs and liabilities to us or inhibit sales of our products.

Personal privacy and data security have become significant issues in the United States, Europe, and in many other jurisdictions where we offer our products. The regulatory framework for privacy and security issues worldwide is rapidly evolving and is likely to remain uncertain for the foreseeable future. Many federal, state, and foreign government bodies and agencies have adopted, or are considering adopting, laws and regulations regarding the collection, use, and disclosure of personal information. In the United States, these include rules and regulations promulgated under the authority of federal

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agencies and state attorneys general and consumer protection agencies. Internationally, virtually every jurisdiction in which we operate has established its own data security and privacy legal framework with which we or our customers must comply, including the Directive, and data protection legislation of the individual member states subject to the Directive. In May 2018, the Directive will be replaced with the GDPR, which will impose additional obligations and risks upon our business. In many jurisdictions enforcement actions and consequences for non-compliance are also rising.

Failure to comply with data protection regulations may result in data protection authorities and other privacy regimes imposing additional obligations to obtain consent from data subjects by or on behalf of our customers. Additionally, the inability to guarantee compliance or otherwise provide acceptable privacy assurances may inhibit the sale and use of our software in the European Union and certain other markets, which could, were it to occur, harm our business and operating results.

In addition to government regulation, privacy advocates and industry groups may propose new and different self-regulatory standards that either legally or contractually apply to us. Further, our customers may require us to comply with more stringent privacy and data security contractual requirements.

Because the interpretation and application of many privacy and data protection laws (including the GDPR), commercial frameworks, and standards are uncertain, it is possible that these laws, frameworks, and standards may be interpreted and applied in a manner that is inconsistent with our existing data management practices or the features of our products. If so, in addition to the possibility of fines, lawsuits, breach of contract claims, and other claims and penalties, we could be required to fundamentally change our business activities and practices or modify our products, which could have an adverse effect on our business. Any inability to adequately address privacy and security concerns, even if unfounded, or comply with applicable privacy and security or data security laws, regulations, and policies, could result in additional cost and liability to us, damage our reputation, inhibit sales, and adversely affect our business.

Furthermore, the costs of compliance with, and other burdens imposed by, the laws, regulations, and policies that are applicable to the businesses of our customers may limit the use and adoption of, and reduce the overall demand for, our products. Privacy and data security concerns, whether valid or not valid, may inhibit market adoption of our products, particularly in certain industries and foreign countries.

We may be sued by third parties for alleged infringement of their proprietary rights.

There is considerable patent and other intellectual property development activity in our industry. Our future success depends in part on not infringing upon the intellectual property rights of others. From time to time, our competitors or other third parties may claim that we are infringing upon their intellectual property rights, and we may be found to be infringing upon such rights. We may receive claims from third parties, including our competitors, that our products and underlying technology infringe or violate a third party’s intellectual property rights, and we may be found to be infringing upon such rights. We may be unaware of the intellectual property rights of others that may cover some or all of our technology. Any claims or litigation could cause us to incur significant expenses and, if successfully asserted against us, could require that we pay substantial damages or ongoing royalty payments, prevent us from offering one or more of our products, or require that we comply with other unfavorable terms. We may also be obligated to indemnify our customers or business partners in connection with any such litigation and to obtain licenses, modify our products, or refund subscription fees, which could further exhaust our resources. In addition, we may incur substantial costs to resolve claims or litigation, whether or not successfully asserted against us, which could include payment of significant settlement, royalty, or license fees, modification of our products, or refunds to customers of subscription fees. Even if we were to prevail in the event of claims or litigation against us, any claim or litigation regarding our intellectual property could be costly and time-consuming and divert the attention of our management and other employees from our business operations. Such disputes could also disrupt our products, adversely impacting our customer satisfaction and ability to attract customers.

Indemnity provisions in various agreements potentially expose us to substantial liability for intellectual property infringement and other losses.

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Our agreements with customers and other third parties may include indemnification or other provisions under which we agree to indemnify or otherwise be liable to them for losses suffered or incurred as a result of claims of intellectual property infringement, damages caused by us to property or persons, or other liabilities relating to or arising from our products or other acts or omissions. The term of these contractual provisions often survives termination or expiration of the applicable agreement. Large indemnity payments or damage claims from contractual breach could harm our business, operating results, and financial condition. From time to time, customers require us to indemnify or otherwise be liable to them for breach of confidentiality or failure to implement adequate security measures with respect to their data stored, transmitted, or processed by our products and customer service platform. Although we normally contractually limit our liability with respect to such obligations, we may still incur substantial liability related to them. Any dispute with a customer with respect to such obligations could have adverse effects on our relationship with that customer and other current and prospective customers, reduce demand for our products, and harm our business and operating results.

Our use of “open source” software could negatively affect our ability to sell our products and subject us to possible litigation.

We use open source software in our products and expect to continue to use open source software in the future. We may face claims from others claiming ownership of, or seeking to enforce the terms of, an open source license, including by demanding release of the open source software, derivative works, or our proprietary source code that was developed using such software. These claims could also result in litigation, require us to purchase a costly license, or require us to devote additional research and development resources to change our products, any of which would have a negative effect on our business and operating results. In addition, if the license terms for the open source software we utilize change, we may be forced to reengineer our products or incur additional costs. Although we have implemented policies to regulate the use and incorporation of open source software into our products, we cannot be certain that we have not incorporated open source software in our products in a manner that is inconsistent with such policies.

Any failure to protect our intellectual property rights could impair our ability to protect our proprietary technology and our brand.

Our success and ability to compete depend in part upon our intellectual property. We currently have two issued patents and have a limited number of patent applications, none of which may result in an issued patent. We primarily rely on copyright, trade secret, and trademark laws, trade secret protection, and confidentiality or license agreements with our employees, customers, partners, and others to protect our intellectual property rights. However, the steps we take to protect our intellectual property rights may be inadequate.

In order to protect our intellectual property rights, we may be required to spend significant resources to monitor and protect these rights. Litigation brought to protect and enforce our intellectual property rights could be costly, time-consuming, and distracting to management, and could result in the impairment or loss of portions of our intellectual property. Furthermore, our efforts to enforce our intellectual property rights may be met with defenses, counterclaims, and countersuits attacking the validity and enforceability of our intellectual property rights. Our failure to secure, protect, and enforce our intellectual property rights could adversely affect our brand and adversely impact our business.

We may not be able to secure additional financing on favorable terms, or at all, to meet our future capital needs.

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We have funded our operations since inception primarily through sales of equity securities, capital lease arrangements, loans for equipment, and subscription payments by our customers for use of our products. We do not know when or if our operations will generate sufficient cash to fund our ongoing operations. In the future, we may require additional capital to respond to business opportunities, challenges, acquisitions, a decline in the level of subscriptions for our products, or unforeseen circumstances. We may not be able to timely secure additional debt or equity financing on favorable terms, or at all. Any debt financing obtained by us could involve restrictive covenants relating to financial and operational matters, which may make it more difficult for us to obtain additional capital and to pursue business opportunities, including potential acquisitions. Additionally, we may not be able to generate sufficient cash to service any debt financing obtained by us, which may force us to reduce or delay capital expenditures or sell assets or operations. If we raise additional funds through further issuances of equity, convertible debt securities, or other securities convertible into equity, our existing stockholders could suffer significant dilution in their percentage ownership of our company, and any new equity securities we issue could have rights, preferences, and privileges senior to those of holders of our common stock. If we are unable to obtain adequate financing or financing on terms satisfactory to us, when we require it, our ability to continue to grow or support our business and to respond to business challenges could be significantly limited.

We face exposure to foreign currency exchange rate fluctuations.

As our international operations expand, our exposure to the effects of fluctuations in currency exchange rates grows. While we have primarily transacted with customers in U.S. dollars historically, we expect to continue to expand the number of transactions with our customers that are denominated in foreign currencies in the future. Fluctuations in the value of the U.S. dollar and foreign currencies may make our subscriptions more expensive for international customers, which could harm our business. Additionally, we incur expenses for employee compensation and other operating expenses at our non-U.S. locations in the local currency for such locations. Fluctuations in the exchange rates between the U.S. dollar and other currencies could result in an increase to the U.S. dollar equivalent of such expenses. These fluctuations could cause our results of operations to differ from our expectations or the expectations of our investors. Additionally, such foreign currency exchange rate fluctuations could make it more difficult to detect underlying trends in our business and results of operations.

Our international subsidiaries maintain net assets that are denominated in currencies other than the functional operating currencies of these entities. Accordingly, changes in the value of foreign currencies relative to the U.S. dollar can affect our operating results due to transactional and translational remeasurements that are reflected in our results of operations. To the extent that fluctuations in foreign currency exchange rates cause our results of operations to differ from our expectations or the expectations of our investors, the trading price of our common stock could be adversely affected.

We currently operate a hedging program to mitigate the impact of foreign currency exchange rate fluctuations on our cash flows and earnings. The use of such hedging activities may not offset any or more than a portion of the adverse financial effects of unfavorable movements in foreign currency exchange rates over the limited time the hedges are in place. Moreover, the use of hedging instruments may introduce additional risks if we are unable to structure effective hedges with such instruments, which could adversely affect our financial condition and operating results.

Taxing authorities may successfully assert that we should have collected or in the future should collect sales and use, value added, or similar taxes, and we could be subject to liability with respect to past or future sales, which could adversely affect our results of operations.

We do not collect sales and use, value added, or similar taxes in all jurisdictions in which we have sales, based on our understanding that such taxes are not applicable. Sales and use, value added, and similar tax laws and rates vary greatly by jurisdiction. Certain jurisdictions in which we do not collect such taxes may assert that such taxes are applicable, which could result in tax assessments, penalties, and interest, and we may be required to collect such taxes in the future. Such tax assessments, penalties, and interest, or future requirements may adversely affect our results of operations.

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Our international operations subject us to potentially adverse tax consequences.

We were founded in Denmark in 2007 and were headquartered in Denmark until we reincorporated in Delaware in 2009. Today, we generally conduct our international operations through subsidiaries and report our taxable income in various jurisdictions worldwide based upon our business operations in those jurisdictions. Our intercompany relationships and transactions are subject to complex regulations, including transfer pricing regulations administered by taxing authorities in various jurisdictions. Our tax returns are generally subject to examination by taxing authorities and the relevant taxing authorities may disagree with our determinations as to the value of assets sold or acquired or income and expenses attributable to specific jurisdictions or transactions. If such a disagreement were to occur, and our position were not sustained, we could be required to pay additional taxes, interest, and penalties, which could result in one-time tax charges, higher effective tax rates, reduced cash flows, and lower overall profitability of our operations.

Additionally, tax laws are dynamic and subject to change as new laws are passed and new interpretations of the law are issued or applied. The United States recently enacted significant tax reform, and certain provisions of the new law may potentially adversely affect us in the future. In addition, governmental tax authorities are increasingly scrutinizing the tax positions of companies. Many countries in the European Union, as well as a number of other countries and organizations such as the Organization for Economic Cooperation and Development, are actively considering changes to existing tax laws that, if enacted, could increase our tax obligations in countries where we do business. If U.S. or other foreign tax authorities change applicable tax laws, our overall taxes could increase, and our business, financial condition, or results of operations may be adversely impacted.

If our goodwill or intangible assets become impaired, we may be required to record a significant charge to earnings.

We review our intangible assets for impairment when events or changes in circumstances indicate the carrying value may not be recoverable. Goodwill is required to be tested for impairment at least annually. As of December 31, 2017, we had a net balance of $67.0 million of goodwill and intangible assets related to prior acquisitions. An adverse change in market conditions, particularly a change resulting in a significant decrease in our share price, or if such change has the effect of changing one of our critical assumptions or estimates, could result in a change to the estimation of fair value that could result in an impairment charge to our goodwill or intangible assets. Any such charges may have a material negative impact on our operating results.

Our ability to use our net operating losses to offset future taxable income may be subject to certain limitations.

As of December 31, 2017, we had federal and state net operating loss carryforwards, or NOLs, of $464.5 million and $218.4 million, respectively, due to prior period losses. In general, under Section 382 of the Internal Revenue Code of 1986, as amended, or the Code, a corporation that undergoes an “ownership change” is subject to limitations on its ability to utilize its NOLs to offset future taxable income. Our existing NOLs may be subject to limitations arising from previous ownership changes, including in connection with our initial public offering or our follow-on public offering. Future changes in our stock ownership, some of which are outside of our control, could result in an ownership change under Section 382 of the Code. Furthermore, our ability to utilize NOLs of companies that we may acquire in the future may be subject to limitations. There is also a risk that due to regulatory changes, such as suspensions on the use of NOLs, or other unforeseen reasons, our existing NOLs could expire or otherwise be unavailable to offset future income tax liabilities. In addition, under the Tax Cuts and Jobs Act, or the Tax Act, the amount of NOLs that we are permitted to deduct in any taxable year is limited to 80% of our taxable income in such year, where taxable income is determined without regard to the NOL deduction itself. There is a risk that due to changes under the Tax Act, regulatory changes, or other unforeseen reasons, our existing NOLs could expire or otherwise be unavailable to offset future income tax liabilities. For these reasons, we may not be able to realize a tax benefit from the use of our NOLs, whether or not we attain profitability.

Our estimates of market opportunity and forecasts of market growth may prove to be inaccurate, and even if the market in which we compete achieves the forecasted growth, our business could fail to grow at similar rates, if at all.

Market opportunity estimates and growth forecasts are subject to significant uncertainty and are based on assumptions and estimates that may not prove to be accurate. Our estimates and forecasts relating to the size and expected growth of the customer relationship management market may prove to be inaccurate. Even if the market in which we compete meets our size estimates and forecasted growth, our business could fail to grow at similar rates, if at all.

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We depend and rely upon SaaS technologies from third parties to operate our business and interruptions or performance problems with these technologies may adversely affect our business and operating results.

We rely heavily on hosted SaaS applications from third parties in order to operate critical functions of our business, including billing and order management, enterprise resource planning, and financial accounting services. If these services become unavailable due to extended outages or interruptions, or because they are no longer available on commercially reasonable terms, our expenses could increase, our ability to manage finances could be interrupted and our processes for managing sales of our products and supporting our customers could be impaired until equivalent services, if available, are identified, obtained, and implemented, all of which could adversely affect our business.

Changes in laws and regulations related to the Internet or changes in the Internet infrastructure itself may diminish the demand for our products, cause us to incur additional expenses, or otherwise have a negative impact on our business.

The future success of our business depends upon the continued use of the Internet as a primary medium for commerce, communication, and business applications. Federal, state, or foreign government bodies or agencies have in the past adopted, and may in the future adopt, laws or regulations affecting the use of the Internet as a commercial medium. Changes in these laws or regulations could require us to modify our products in order to comply with these changes or substantially increase costs associated with the operation of our products. Additionally, the adoption of any laws, regulations, or practices limiting Internet neutrality could allow Internet service providers to block, degrade, or interfere with our products or services. These laws, regulations, or practices could decrease the demand for, or the usage of, our products and services, increase our cost of doing business, and adversely affect our operating results. In addition, government agencies or private organizations have imposed and may impose additional taxes, fees, or other charges for accessing the Internet or commerce conducted via the Internet. These laws or charges could limit the growth of Internet-related commerce or communications generally, or result in reductions in the demand for Internet-based platforms and services such as ours. In addition, the use of the Internet as a business tool could be adversely affected due to delays in the development or adoption of new standards and protocols to handle increased demands of Internet activity, security, reliability, cost, ease-of-use, accessibility, and quality of service. The performance of the Internet and its acceptance as a business tool has been adversely affected by “viruses,” “malware,” and similar malicious programs and the Internet has experienced a variety of outages and other delays as a result of damage to portions of its infrastructure.

Catastrophic events may disrupt our business.

Our corporate headquarters are located in San Francisco, California and we operate in or utilize hosting services that are located in North America, Europe, Asia and Australia. Key features and functionality of our products are enabled by third parties that are headquartered in California and operate in or utilize data centers in the United States and Europe. Additionally, we rely on our network and third-party infrastructure and enterprise applications, internal technology systems, and our website for our development, marketing, operational support, hosted services, and sales activities. In the event of a major earthquake, hurricane, or catastrophic event such as fire, flood, power loss, telecommunications failure, cyber-attack, war, or terrorist attack, we may be unable to continue our operations and may endure system interruptions, reputational harm, delays in our application development, lengthy interruptions in our products, breaches of data security, and loss of critical data, all of which could have an adverse effect on our future operating results.

Exposure to United Kingdom political developments, including the United Kingdom’s vote to leave the European Union, could have a material adverse effect on us.

On June 23, 2016, a referendum was held on the United Kingdom’s membership in the European Union, the outcome of which was a vote in favor of leaving the European Union. The United Kingdom’s vote to leave the European Union creates an uncertain political and economic environment in the United Kingdom and potentially across other European Union member states, which may last for a number of months or years.

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The result of the referendum means that the long-term nature of the United Kingdom’s relationship with the European Union is unclear and that there is considerable uncertainty as to when any such relationship will be agreed and implemented. In the interim, there is a risk of instability for both the United Kingdom and the European Union, which could adversely affect our results, financial condition, and prospects.

The political and economic instability created by the United Kingdom’s vote to leave the European Union has caused and may continue to cause significant volatility in global financial markets and the value of the British Pound Sterling currency or other currencies, including the Euro. Depending on the terms reached regarding any exit from the European Union, it is possible that there may be adverse practical or operational implications on our business.

The outcome of the referendum has also created uncertainty with regard to the regulation of data protection in the United Kingdom. In particular, it is unclear how the United Kingdom’s vote to leave the European Union will affect the United Kingdom’s enactment of the European General Data Protection Regulation, and how data transfers to and from the United Kingdom will be regulated.

Risks Related to Ownership of Our Common Stock

Our stock price has been, and may continue to be, volatile or may decline regardless of our operating performance, resulting in substantial losses for our stockholders.

The trading price of our common stock has been, and may continue to be, volatile and could fluctuate widely regardless of our operating performance. The market price of our common stock may fluctuate significantly in response to numerous factors, many of which are beyond our control, including:

In addition, the stock markets have experienced extreme price and volume fluctuations that have affected and continue to affect the market prices of equity securities of many technology companies. Stock prices of many technology companies

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have fluctuated in a manner unrelated or disproportionate to the operating performance of those companies. In the past, stockholders have instituted securities class action litigation following periods of market volatility. If we were to become involved in securities litigation, it could subject us to substantial costs, divert resources and the attention of management from operating our business, and adversely affect our business, results of operations, financial condition, and cash flows.

Our directors, officers, and principal stockholders beneficially own a significant percentage of our stock and will be able to exert significant influence over matters subject to stockholder approval.

As of December 31, 2017, our directors, officers, five percent or greater stockholders, and their respective affiliates beneficially owned in the aggregate approximately 41% of our outstanding common stock. As a result, these stockholders have the ability to influence us through this ownership position. These stockholders may be able to exert significant influence in matters requiring stockholder approval. For example, these stockholders may be able to exert significant influence in elections of directors, amendments of our organizational documents, and approval of any merger, sale of assets, or other major corporate transaction. This may prevent or discourage unsolicited acquisition proposals or offers for our common stock that you may feel are in your best interest as one of our stockholders.

Substantial future sales of shares of our common stock could cause the market price of our common stock to decline.

The market price of our common stock could decline as a result of substantial sales of our common stock, particularly sales by our directors, executive officers, and significant stockholders, or the perception in the market that holders of a large number of shares intend to sell their shares.

Additionally, the shares of common stock subject to outstanding options and restricted stock unit awards under our equity incentive plans and the shares reserved for future issuance under our equity incentive plans will become eligible for sale in the public market in the future, subject to certain legal and contractual limitations.

Certain holders of our common stock have rights, subject to some conditions, to require us to file registration statements covering their shares or to include their shares in registration statements that we may file for ourselves or our stockholders.

Anti-takeover provisions in our charter documents and under Delaware law could make an acquisition of our company more difficult, limit attempts by our stockholders to replace or remove our current management, and limit the market price of our common stock.

Provisions in our certificate of incorporation and bylaws may have the effect of delaying or preventing a change of control or changes in our management. Our certificate of incorporation and bylaws include provisions that:

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These provisions may frustrate or prevent any attempts by our stockholders to replace or remove our current management by making it more difficult for stockholders to replace members of our board of directors, which is responsible for appointing the members of our management. In addition, because we are incorporated in Delaware, we are governed by the provisions of Section 203 of the General Corporation Law of the State of Delaware, which generally prohibits a Delaware corporation from engaging in any of a broad range of business combinations with any “interested” stockholder for a period of three years following the date on which the stockholder became an “interested” stockholder. Any delay or prevention of a change of control transaction or changes in our management could cause the market price of our common stock to decline.

The requirements of being a public company may strain our resources, divert management’s attention, and affect our ability to attract and retain executive management and qualified board members.

As a public company, we are subject to the reporting requirements of the Exchange Act, the Sarbanes-Oxley Act, the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010, the listing requirements of the exchanges and other markets upon which our common stock is listed, and other applicable securities rules and regulations. Compliance with these rules and regulations increase our legal and financial compliance costs, make some activities more difficult, time-consuming, or costly, and increase demand on our systems and resources. The Exchange Act requires, among other things, that we file annual, quarterly, and current reports with respect to our business and operating results. The Sarbanes-Oxley Act requires, among other things, that we maintain effective disclosure controls and procedures and internal control over financial reporting. In order to maintain and, if required, improve our disclosure controls and procedures and internal control over financial reporting to meet this standard, significant resources and management oversight may be required. We are required to disclose changes made in our internal control and procedures on a quarterly basis and to furnish a report by management on, among other things, the effectiveness of our internal control over financial reporting. As a result of the complexity involved in complying with the rules and regulations applicable to public companies, our management’s attention may be diverted from other business concerns, which could adversely affect our business and operating results. Although we have already hired additional employees to assist us in complying with these requirements, we may need to hire more employees in the future or engage outside consultants, which will increase our operating expenses.

In addition, changing laws, regulations, and standards relating to corporate governance and public disclosure are creating uncertainty for public companies, increasing legal and financial compliance costs, and making some activities more time consuming. These laws, regulations, and standards are subject to varying interpretations, in many cases due to their lack of specificity, and, as a result, their application in practice may evolve over time as new guidance is provided by regulatory and governing bodies. This could result in continuing uncertainty regarding compliance matters and higher costs necessitated by ongoing revisions to disclosure and governance practices. We intend to invest substantial resources to comply with evolving laws, regulations, and standards, and this investment may result in increased general and administrative expenses and a diversion of management’s time and attention from business operations to compliance activities. If our efforts to comply with new laws, regulations, and standards differ from the activities intended by regulatory or governing bodies due to ambiguities related to their application and practice, regulatory authorities may initiate legal proceedings against us and our business may be adversely affected.

Being a public company and these new rules and regulations have made it more expensive for us to obtain director and officer liability insurance, and in the future we may be required to accept reduced coverage or incur substantially higher costs to obtain coverage. These factors could also make it more difficult for us to attract and retain qualified members of our board of directors, particularly to serve on our audit committee and compensation committee, and qualified executive officers.

As a result of disclosure of information in our filings with the SEC, our business and financial condition have become more visible, which we believe may result in threatened or actual litigation, including by competitors and other third parties. If such claims are successful, our business and operating results could be adversely affected, and even if the claims do not result in litigation or are resolved in our favor, these claims, and the time and resources necessary to resolve them, could divert the resources of our management and adversely affect our business and operating results.

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We do not intend to pay dividends on our common stock so any returns will be limited to changes in the value of our common stock.

We have never declared or paid any cash dividends on our common stock. We currently anticipate that we will retain future earnings for the development, operation, and expansion of our business, and do not anticipate declaring or paying any cash dividends for the foreseeable future. In addition, our ability to pay cash dividends on our common stock may be prohibited or limited by the terms of our future debt financing arrangements. Any return to stockholders will therefore be limited to the increase, if any, of our stock price, which may never occur.

If securities or industry analysts do not continue to publish research or publish inaccurate or unfavorable research about our business, our stock price and trading volume could decline.

The trading market for our common stock depends in part on the research and reports that securities or industry analysts publish about us or our business. If one or more of the analysts who cover us downgrade our common stock or publish inaccurate or unfavorable research about our business, our common stock price would likely decline. If one or more of these analysts cease coverage of us or fail to publish reports on us regularly, demand for our common stock could decrease, which might cause our common stock price and trading volume to decline.

Our charter documents designate the Court of Chancery of the State of Delaware as the sole and exclusive forum for certain types of actions and proceedings that may be initiated by our stockholders, which could limit our stockholders’ ability to obtain a favorable judicial forum for disputes with us or our directors, officers, or other employees.

Our certificate of incorporation and bylaws provide that, unless we consent in writing to the selection of an alternative forum, the Court of Chancery of the State of Delaware shall be the sole and exclusive forum for (A) any derivative action or proceeding brought on our behalf, (B) any action asserting a claim of breach of a fiduciary duty owed by any of our directors, officers, or other employees to us or our stockholders, (C) any action asserting a claim arising pursuant to any provision of the General Corporation Law of the State of Delaware, our certificate of incorporation, or our bylaws, or (D) any action asserting a claim against us governed by the internal affairs doctrine. Any person or entity purchasing or otherwise acquiring any interest in shares of our capital stock shall be deemed to have notice of and consented to the provisions of our certificate of incorporation described above. This choice of forum provision may limit a stockholder’s ability to bring a claim in a judicial forum that it finds favorable for disputes with us or our directors, officers, or other employees, which may discourage such lawsuits against us and our directors, officers, and other employees. Alternatively, if a court were to find these provisions of our certificate of incorporation inapplicable to, or unenforceable in respect of, one or more of the specified types of actions or proceedings, we may incur additional costs associated with resolving such matters in other jurisdictions, which could adversely affect our business, financial condition, or results of operations.

None.

Our corporate headquarters are located in San Francisco, California. We operate in San Francisco under four leases for approximately 72,900, 52,000, 34,900, and 18,000 square feet of space, respectively. These leases expire in August 2022, October 2023, October 2019, and January 2021, respectively.

We also lease office space in various locations in North America, South America, Europe, Australia, and Asia. We intend to procure additional space as we add employees and expand geographically. We believe our facilities are adequate and sufficient for our current needs and that, should it be needed, suitable additional or alternative space will be available to accommodate any such expansion of our operations.

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From time to time, we may be subject to legal proceedings, claims, investigations, and government inquires in the ordinary course of business. We have received, and may in the future continue to receive, claims from third parties asserting, among other things, infringement of their intellectual property rights, defamation, privacy, and contractual rights. Legal risk is enhanced in certain jurisdictions outside the United States where our protection from liability for content added to our products by third parties may be unclear and where we may be less protected under local laws than we are in the United States. Future litigation may be necessary to defend ourselves, our partners, and our customers by determining the scope, enforceability, and validity of third-party proprietary rights, or to establish our proprietary rights. The results of any current or future litigation cannot be predicted with certainty, and regardless of the outcome, litigation can have an adverse impact on us because of defense and settlement costs, diversion of management resources, and other factors.

Not Applicable.

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PART II

Item 5. Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities.

Market Information for Common Stock

Our common stock has been listed on the New York Stock Exchange under the symbol “ZEN” since May 15, 2014, the date of our initial public offering.

The following table sets forth for the indicated periods the high and low intra-day sales prices of our common stock as reported by the New York Stock Exchange.

Stock Performance Graph

The following stock performance graph and related information shall not be deemed “soliciting material” or to be “filed” with the SEC, nor shall such information be incorporated by reference into any future filing under the Securities Act of 1933, as amended, or Exchange Act, except to the extent that we specifically incorporate it by reference into such filing.

The following stock performance graph compares total stockholder returns for Zendesk, Inc. from May 15, 2014, the date of our initial public offering, through December 31, 2017, against the S&P 500 Index and the S&P 500 Composite/Software, assuming a $100 investment made on May 15, 2014. Each of the two comparative measures of cumulative total return assumes reinvestment of dividends. The stock performance shown in the graph below is not necessarily indicative of future price performance.

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Holders

As of December 31, 2017, there were approximately 38 holders of record of our common stock. However, because many of our shares of common stock are held by brokers and other institutions on behalf of stockholders, we are unable to accurately estimate the total number of stockholders represented by these record holders.

Dividends

We have never declared or paid any cash dividend on our capital stock. We currently intend to retain any future earnings and do not expect to pay any dividends in the foreseeable future. Any future determination to declare cash dividends will be made at the discretion of our board of directors, subject to applicable laws, and will depend on a number of factors, including our financial condition, operating results, capital requirements, contractual restrictions, general business conditions, and other factors that our board of directors may deem relevant.

Issuer Purchases of Equity Securities

No shares of our common stock were repurchased during the three months ended December 31, 2017.

Securities Authorized for Issuance Under Equity Compensation Plans

See Item 12, “Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters” for information regarding securities authorized for issuance.

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The consolidated statements of operations data and the consolidated balance sheets data are derived from our audited consolidated financial statements and should be read together with “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” our consolidated financial statements, and the related notes included elsewhere in this Annual Report on Form 10-K. Our historical data results are not necessarily indicative of our results in any future period.

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MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION

AND RESULTS OF OPERATIONS

The following discussion and analysis of our financial condition and results of operations should be read in conjunction with the section titled “Selected Consolidated Financial Data” and consolidated financial statements and related notes thereto included elsewhere in this Annual Report on Form 10-K. This discussion contains forward-looking statements that involve risks and uncertainties. Our actual results could differ materially from those discussed below. Factors that could cause or contribute to such differences include, but are not limited to, those identified below and those discussed in the section titled “Risk Factors” included elsewhere in this Annual Report on Form 10-K.

Overview

We are a software development company that provides SaaS products that are intended to help organizations and their customers build better relationships. Our product family is built upon a modern architecture that enables us and our customers to rapidly innovate, adapt our technology in novel ways, and easily integrate with other products and applications. With our origins in customer service, we have evolved our offerings over time to a family of products that work together to help organizations understand their customers, improve communications across all channels, and engage where and when it’s needed most.

We believe in developing products that serve organizations of all sizes and across all industries. The flagship product in our family, Zendesk Support, provides organizations with the ability to track, prioritize, and solve customer support tickets across multiple channels, bringing customer information and interactions into one place. Our other widely available products integrate with Support and include Zendesk Chat, Zendesk Talk, and Zendesk Guide. Chat is live chat software that provides a fast and responsive way for organizations to connect with their customers. Talk is cloud-based call center software that facilitates personal and productive phone support conversations between organizations and their customers. Guide is a self-service destination that organizations can use to provide articles, interactive forums, and a community that help an organization’s customers help themselves. We offer a range of subscription account plans for our products that vary in price based on functionality, type, and, for Support and Chat, the amount of product support we offer. We also offer a range of additional features that customers can purchase and add to their subscriptions.

For the years ended December 31, 2017, 2016, and 2015, our revenue was $430.5 million, $312.0 million, and $208.8 million, respectively, representing a 38% growth rate from 2016 to 2017 and a 49% growth rate from 2015 to 2016. For the years ended December 31, 2017, 2016, and 2015 we derived $200.8 million, or 47%, $143.5 million, or 46%, and $92.5 million, or 44%, respectively, of our revenue from customers located outside of the United States. We expect that the rate of growth in our revenue will decline as our business scales, even if our revenue continues to grow in absolute terms. For the years ended December 31, 2017, 2016, and 2015, we generated net losses of $110.6 million, $103.8 million, and $84.1 million, respectively.

The growth of our business and our future success depend on many factors, including our ability to continue to innovate, develop a unified omnichannel customer experience, build brand recognition and a scalable product for larger enterprises, maintain our leadership in the small and medium-sized business, or SMB, market, add new customers, generate additional revenue from our existing customer base, and increase our global customer footprint. While these areas represent significant opportunities for us, we also face significant risks and challenges that we must successfully address in order to sustain the growth of our business and improve our operating results. We anticipate that we will continue to expand our operations and headcount in the near term. The expected addition of new personnel and the expenditures that we anticipate will be necessary to manage our anticipated growth, including expenditures relating to hosting capabilities, leasehold improvements, and related fixed assets, will make it more difficult for us to achieve profitability in the near term. Many of these investments will occur in advance of us experiencing any direct benefit and will make it difficult to determine if we are allocating our resources efficiently.

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We have focused on rapidly growing our business and plan to continue to invest for long-term growth. We expect to continue to develop our hosting capabilities primarily through expenditures for third-party managed hosting services. Additionally, we expect to incur depreciation expense and related costs associated with our self-managed colocation data centers while we transition our primary data center usage to third-party managed hosting services. The amount and timing of these disbursements will vary based on our estimates of projected growth and planned use of hosting resources. Over time, we anticipate that we will continue to gain economies of scale by efficiently utilizing our hosting and personnel resources to support the growth in our number of customers. We also expect to continue to grow our customer experience organization, resulting in additional salary and share-based compensation expenses. In addition, we expect to incur amortization expense associated with acquired intangible assets and capitalized internal-use software. As a result, we expect our gross margin to improve in the long-term, although our gross margin may decrease in the near-term and may vary from period to period as our revenue fluctuates and as a result of the timing and amount of such costs.

We expect our operating expenses to continue to increase in absolute dollars in future periods. We have invested, and expect to continue to invest, in our software development efforts to broaden the functionality of our existing products, to further integrate these products and services, and to introduce new products. We plan to continue to expand our sales and marketing organizations, particularly in connection with our efforts to expand our customer base. We also expect to continue to incur additional general and administrative costs in order to support the growth of our business and the infrastructure required to comply with our obligations as a public company.

Key Business Metrics

We review a number of operating metrics, including the following key metrics, to evaluate our business, measure our performance, identify trends affecting our business, formulate business plans, and make strategic decisions.

Number of Paid Customer Accounts. We believe that our ability to increase our number of paid accounts using our products is an indicator of our market penetration, the growth of our business, and our potential future business opportunities. We define the number of paid customer accounts as the sum of the number of accounts on Zendesk Support, exclusive of our legacy Starter plan, free trials or other free services, the number of accounts on Chat, exclusive of free trials or other free services, and the number of accounts on all of our other products, exclusive of free trials and other free services, each as of the end of the period and as identified by a unique account identifier. Use of Support, Chat, and our other products requires separate subscriptions and each of these accounts are treated as a separate paid customer account. Existing customers may also expand their utilization of our products by adding new accounts and a single consolidated organization or customer may have multiple accounts across each of our products to service separate subsidiaries, divisions, or work processes. Each of these accounts is also treated as a separate paid customer account. An increase in the number of paid customer accounts generally correlates to an increase in the number of authorized agents licensed to use our products, which directly affects our revenue and results of operations. We view growth in this metric as a measure of our success in converting new sales opportunities. We had approximately 118,900 paid customer accounts as of December 31, 2017, including approximately 64,100 paid customer accounts on Support, approximately 47,000 paid customer accounts on Chat, and approximately 7,800 paid customer accounts on our other products. As the total number of paid customer accounts increases, we expect the rate of growth in the number of paid customer accounts to decline.

Dollar-Based Net Expansion Rate. Our ability to generate revenue is dependent upon our ability to maintain our relationships with our customers and to increase their utilization of our products. We believe we can achieve this by focusing on delivering value and functionality that retains our existing customers, expands the number of authorized agents associated with an existing paid customer account, and results in upgrades to higher-priced subscription plans and the purchase of additional products. Maintaining customer relationships allows us to sustain and increase revenue to the extent customers maintain or increase the number of authorized agents licensed to use our products. We assess our performance in this area by measuring our dollar-based net expansion rate. Our dollar-based net expansion rate provides a measurement of our ability to increase revenue across our existing customer base through expansion of authorized agents associated with paid customer accounts, upgrades in subscription plans, and the purchase of additional products as offset by churn, contraction in authorized agents associated with paid customer accounts, and downgrades in subscription plans. We do not currently incorporate operating metrics associated with our analytics product or our Outbound product into our measurement of dollar-based net expansion rate.

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Our dollar-based net expansion rate is based upon our monthly recurring revenue for a set of paid customer accounts on our products. Monthly recurring revenue for a paid customer account is a legal and contractual determination made by assessing the contractual terms of each paid customer account, as of the date of determination, as to the revenue we expect to generate in the next monthly period for that paid customer account, assuming no changes to the subscription and without taking into account any one-time discounts or any usage above the subscription base, if any, that may be applicable to such subscription. Monthly recurring revenue is not determined by reference to historical revenue, deferred revenue, or any other United States Generally Accepted Accounting Principles, or GAAP, financial measure over any period. It is forward-looking and contractually derived as of the date of determination. We calculate our dollar-based net expansion rate by dividing our retained revenue net of contraction and churn by our base revenue. We define our base revenue as the aggregate monthly recurring revenue across our products from the paid customer accounts on Support and Chat as of the date one year prior to the date of calculation. We define our retained revenue net of contraction and churn as the aggregate monthly recurring revenue across our products from the same customer base included in our measure of base revenue at the end of the annual period being measured. Our dollar-based net expansion rate is also adjusted to eliminate the effect of certain activities that we identify involving the transfer of agents between paid customer accounts, consolidation of customer accounts, or the split of a single paid customer account into multiple paid customer accounts. In addition, our dollar-based net expansion rate is adjusted to include paid customer accounts in the customer base used to determine retained revenue net of contraction and churn that share common corporate information with customers in the customer base that is used to determine our base revenue. Giving effect to this consolidation results in our dollar-based net expansion rate being calculated across approximately 92,800 customers, as compared to the approximately 118,900 total paid customer accounts as of December 31, 2017. To the extent that we can determine that the underlying customers do not share common corporate information, we do not aggregate paid customer accounts associated with reseller and other similar channel arrangements for the purposes of determining our dollar-based net expansion rate. While not material, we believe the failure to account for these activities would otherwise skew our dollar-based net expansion metrics associated with customers that maintain multiple paid customer accounts across their products, and paid customer accounts associated with reseller and other similar channel arrangements.

Our dollar-based net expansion rate was 119% as of December 31, 2017. We expect that, among other factors, our continued focus on adding larger paid customer accounts at the time of addition and the growth in our revenue will result in an overall decline in our dollar-based net expansion rate over time as our aggregate monthly recurring revenue grows.

Components of Results of Operations

Revenue

We derive substantially all of our revenue from subscription services, which are comprised of subscription fees from customer accounts on Support and, to a lesser extent, Chat, Talk and Guide. Each subscription may have multiple authorized users, and we refer to each user as an “agent.” The number of agents ranges from one to thousands for various customer accounts. Our pricing is generally established on a per agent basis. We offer a range of subscription account plans for our products that vary in price based on functionality, type and, for Support and Chat, the amount of product support we offer. We also offer a range of additional features that customers can purchase and add to their subscriptions. Certain arrangements provide for incremental fees above a fixed maximum number of monthly agents during the subscription term. We sell subscription services under contractual agreements that vary in length, ranging between one month and multiple years, with the majority of subscriptions having a term of either one month or one year.

Subscription fees are generally non-refundable regardless of the actual use of the service. Subscription revenue is typically affected by the number of customer accounts, number of agents, and the type of plan purchased by our customers, and is recognized ratably over the term of the arrangement beginning on the date that our services are made available to our customers. Subscription services purchased online are typically paid for via a credit card on the date of purchase while subscription services purchased through our internal sales organization are generally billed with monthly, quarterly, or annual payment frequencies. Due to our mixed contract lengths and billing frequencies, the annualized value of the arrangements we

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enter into with our customers may not be fully reflected in deferred revenue at any single point in time. Accordingly, we do not believe that the change in deferred revenue for any period is an accurate indicator of future revenue for a given period of time. Additionally, because of the mix of payment frequencies and contract lengths, we do not believe that backlog is a meaningful performance metric.

We derive an immaterial amount of revenue from implementation and training services, for which we recognize revenue upon completion. We also derive an immaterial amount of revenue from Talk, for which we recognize revenue based on usage.

Cost of Revenue, Gross Margin, and Operating Expenses

Cost of Revenue. Cost of revenue consists primarily of personnel costs (including salaries, share-based compensation, and benefits) for employees associated with our infrastructure, product support, and professional service organizations, and expenses for hosting capabilities, including third-party managed hosting services and depreciation from our self-managed colocation data centers. Cost of revenue also includes third party license fees, amortization expense associated with capitalized internal-use software, payment processing fees, amortization expense associated with acquired intangible assets, and allocated shared costs. We allocate shared costs such as facilities, information technology and security costs to all departments based on headcount. As such, allocated shared costs are reflected in cost of revenue and each operating expense category.

We currently operate out of four self-managed colocation data centers, in which we manage our own network equipment and systems, located in California, Virginia, Ireland, and Germany. In addition, we utilize third-party managed hosting facilities located in North America, Europe, Asia and Australia to host our services, support our infrastructure, and support certain research and development functions. We currently intend to continue to operate our self-managed colocation data centers and incur expenditures for third-party managed hosting services over time while we transition our primary data center usage to third-party managed hosting services.

We intend to continue to invest additional resources in our infrastructure, product support, and professional service organizations, organically and through acquisitions. We expect that recent and future business acquisitions will result in increased amortization expense of intangible assets such as acquired technology. As we continue to invest in technology innovation, we expect to continue to incur capitalized internal-use software costs and related amortization. We expect these investments in technology to not only expand the capabilities of our products but also to increase the efficiency of how we deliver these services, enabling us to improve our gross margin over time, although our gross margin may decrease in the near-term and may vary from period to period as our revenue fluctuates and as result of the timing and amount of these investments. To the extent that we continue to rely on third-party technology to provide certain functionality within our products or for certain subscription plans or integrations, we expect third-party license fees for technology that is incorporated in such products and subscription plans to remain significant over time.

Gross Margin. Gross margin is gross profit expressed as a percentage of revenue. Our gross margin may fluctuate from period to period as our revenue fluctuates and as a result of the timing and amount of investments to expand our product support and professional services teams, investments in additional personnel, hosting equipment, and third-party managed hosting facilities to support our infrastructure, increased share-based compensation expense, as well as the amortization of certain acquired intangible assets, costs associated with capitalized internal-use software, and third-party license fees.

Research and Development. Research and development expenses consist primarily of personnel costs (including salaries, share-based compensation, and benefits) for employees associated with our research and development organization and allocated shared costs.

We focus our research and development efforts on the continued development of our products, including the development and deployment of new features and functionality and enhancements to our software architecture and integration across our products. We expect that, in the future, research and development expenses will increase in absolute dollars. However, we expect our research and development expenses to decrease modestly as a percentage of our revenue in the long-term, although this may fluctuate from period to period depending on fluctuations in revenue and the timing and the extent of our research and development expenses.

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Sales and Marketing. Sales and marketing expenses consist of personnel costs (including salaries, commissions, share-based compensation, and benefits) for employees associated with our sales and marketing organizations, costs of marketing activities, and allocated shared costs. Marketing activities include online lead generation, advertising, promotional events, and public and community relations. Sales commissions and other incremental costs to acquire contracts are expensed as incurred.

We focus our sales and marketing efforts on generating awareness of our products, establishing and promoting our brand, and cultivating a community of successful and vocal customers. We plan to continue investing in sales and marketing by increasing the number of sales employees, developing our marketing teams, building brand awareness, and sponsoring additional marketing events, which we believe will enable us to add new customers and increase penetration within our existing customer base. Because we do not have a long history of undertaking or growing many of these activities, we cannot predict whether, or to what extent, our revenue will increase as we invest in these strategies. We expect our sales and marketing expenses to continue to increase in absolute dollars and continue to be our largest operating expense category for the foreseeable future. Our sales and marketing expenses as a percentage of our revenue over time may fluctuate from period to period depending on fluctuations in revenue and the timing and extent of our sales and marketing expenses.

General and Administrative. General and administrative expenses consist primarily of personnel costs (including salaries, share-based compensation, and benefits) for our executive, finance, legal, human resources, and other administrative employees. In addition, general and administrative expenses include fees for third-party professional services, including legal, accounting, and tax related services, other corporate expenses, and allocated shared costs.

We expect to incur incremental costs associated with supporting the growth of our business, both in terms of size and geographic expansion, and the infrastructure required to be a public company. Such costs include increases in our finance, legal, and human resources personnel, additional legal, accounting, tax, and compliance-related services fees, insurance costs, and costs of executing significant transactions, including business acquisitions, and other costs associated with being a public company. As a result, we expect our general and administrative expenses to continue to increase in absolute dollars for the foreseeable future. However, we expect our general and administrative expenses to decrease modestly as a percentage of our revenue in the long-term, although this may fluctuate from period to period depending on fluctuations in revenue and the timing and extent of our general and administrative expenses.

Other Income (Expense), Net

Other income (expense), net consists primarily of interest income from marketable securities and foreign currency gains and losses.

Provision for (Benefit from) Income Taxes

Provision for (benefit from) income taxes consists of federal and state income taxes in the United States and income taxes in certain foreign jurisdictions.

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Results of Operations for Fiscal Years 2017, 2016, and 2015

The following tables set forth our results of operations for the periods presented in dollars and as a percentage of our revenue:

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Revenue

Revenue increased $118.5 million, or 38%, in 2017 compared to 2016. Of the total increase in revenue, $26.1 million, or 22%, was attributable to revenue from new accounts acquired from January 1, 2017 through December 31, 2017, net of churn and contraction, and $92.4 million, or 78%, was attributable to revenue from accounts existing on or before December 31, 2016, net of churn and contraction.

Revenue increased $103.2 million, or 49%, in 2016 compared to 2015. Of the total increase in revenue, $23.7 million, or 23%, was attributable to revenue from new accounts acquired from January 1, 2016 through December 31, 2016, net of churn and contraction, and $79.5 million, or 77%, was attributable to revenue from accounts existing on or before December 31, 2015, net of churn and contraction.

Cost of Revenue and Gross Margin

Cost of revenue increased $33.5 million, or 36%, in 2017 compared to 2016. The overall increase was primarily due to increased hosting costs of $11.7 million, increased employee compensation-related costs of $9.7 million, and increased third-party license fees of $4.9 million. The increase in hosting costs was driven by expenditures for third-party managed hosting services and increased costs, including depreciation expense, related to our self-managed colocation data centers. The increase in employee compensation-related costs was driven by headcount growth. The increase in third-party license fees was driven by increased customer usage of certain product features. Further contributing to the overall increase was an increase in allocated shared costs of $4.3 million, primarily related to facilities and information technology.

Our gross margin increased by 0.5 percentage points in 2017 compared to 2016. The overall improvement was primarily driven by our ability to increase revenue with a more moderate increase in headcount. The overall improvement was partially offset by increased hosting costs due to continued investment in our hosting capabilities.

Cost of revenue increased $26.7 million, or 40%, in 2016 compared to 2015. The overall increase was primarily due to increased employee compensation-related costs of $10.3 million, increased hosting costs of $6.0 million, and increased amortization expense from acquired intangible assets of $1.5 million. The increase in employee compensation-related costs was driven by headcount growth. The increase in hosting costs was driven by increased depreciation expense from investments in our self-managed colocation data centers and expenditures for third-party managed hosting services. The increase in

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amortization expense from acquired intangible assets was related to an acquisition completed in October 2015. Further contributing to the overall increase was an increase in allocated shared costs of $3.5 million, primarily related to facilities and information technology.

Our gross margin increased by 2.1 percentage points in 2016 compared to 2015. The overall improvement was primarily driven by our ability to increase revenue with a more moderate increase in headcount and hosting costs due to improved operational efficiency.

Operating Expenses

Research and Development Expenses

Research and development expenses increased $24.2 million, or 27%, in 2017 compared to 2016. The overall increase was primarily due to increased employee compensation-related costs of $13.8 million, driven by headcount growth, and increased outside services costs of $2.0 million. The increase in outside services costs was primarily attributable to the adaptation of our hosting infrastructure. Further contributing to the overall increase was an increase in allocated shared costs of $4.8 million.

Research and development expenses increased $28.5 million, or 45%, in 2016 compared to 2015. The overall increase was primarily due to increased employee compensation-related costs of $23.5 million, driven by headcount growth, and an increase in allocated shared costs of $4.2 million. The overall increase was partially offset by a reduction of $2.3 million in share-based compensation expense, recognized using the accelerated attribution method, associated with certain awards granted prior to our IPO that vest upon both a service condition and a performance condition, that performance condition being the completion of our IPO.

Sales and Marketing Expenses

Sales and marketing expenses increased $53.8 million, or 32%, in 2017 compared to 2016. The overall increase was primarily due to increased employee compensation-related costs, including commissions, of $25.2 million, driven by headcount growth, and an increase in marketing program costs of $10.8 million. The increase in marketing program costs was driven by increased advertising activities. Further contributing to the overall increase was an increase in allocated shared costs of $8.5 million.

Sales and marketing expenses increased $52.9 million, or 46%, in 2016 compared to 2015. The overall increase was primarily due to increased employee compensation-related costs, including commissions, of $32.5 million, driven by headcount growth, and an increase in marketing program costs of $10.7 million. The increase in marketing program costs was driven by brand awareness trade shows and advertising campaigns. Further contributing to the overall increase was an increase in allocated shared costs of $6.1 million.

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General and Administrative Expenses

General and administrative expenses increased $17.3 million, or 27%, in 2017 compared to 2016. The overall increase was primarily due to increased employee compensation-related costs of $12.6 million, driven by headcount growth, and increased professional and outside services costs of $0.9 million. Further contributing to the overall increase was an increase in allocated shared costs of $1.7 million.

General and administrative expenses increased $16.5 million, or 34%, in 2016 compared to 2015. The overall increase was primarily due to increased employee compensation-related costs of $11.0 million, driven by headcount growth, and increased professional and outside services costs of $2.2 million. Further contributing to the overall increase was an increase in allocated shared costs of $1.5 million.

Quarterly Results of Operations

The following unaudited quarterly results of operations data for each of the eight quarters in the two-year period ended December 31, 2017 have been prepared on a basis consistent with our audited consolidated annual financial statements and include, in management’s opinion, all normal recurring adjustments necessary for the fair presentation of the results of operations data for these periods, in accordance with GAAP. The following quarterly financial data should be read in conjunction with our consolidated financial statements and the related notes included elsewhere in this Annual Report on Form 10-K. The results of historical periods are not necessarily indicative of the results of operations for any future period.

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Quarterly Trends in Revenue and Cost of Revenue

Our quarterly revenue increased sequentially for each period presented, primarily due to sales of new subscriptions to our products and net expansion by our existing customers. We cannot assure you that this pattern of sequential growth in revenue will continue.

Our gross margin in the first quarter of any fiscal year is negatively impacted relative to the preceding fourth quarter due to the fewer number of days in the first quarter over which we record subscription revenue as compared to the preceding fourth quarter and the fact that certain expenses in our cost of revenue are not sensitive to the number of days in the quarter.

Quarterly Trends in Costs and Expenses

Our quarterly costs and expenses increased sequentially for each period presented, primarily due to increased compensation-related costs related to an increase in headcount in connection with the expansion of our business.

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Seasonality

We have experienced, and expect to continue to experience in the future, seasonality in our business, and our operating results and financial condition may be affected by such trends in the future. We generally experience seasonal fluctuations in demand for our products and services, and believe that our quarterly sales are affected by industry buying patterns. For example, we typically have customers who add flexible agents when they need more capacity during busy periods, especially in the fourth quarter, and then subsequently scale back in the first quarter of the following year. We believe that the seasonal trends that we have experienced in the past may continue for the foreseeable future.

Liquidity and Capital Resources

As of December 31, 2017, our principal sources of liquidity were cash, cash equivalents and marketable securities totaling $344.4 million, which were held for working capital purposes. Our cash equivalents and marketable securities are comprised of corporate bonds, money market funds, U.S. Treasury securities, asset-backed securities, commercial paper, and agency securities.

The following table summarizes our cash flows for the periods indicated (in thousands):

To date, we have financed our operations primarily through private and public equity financings and customer payments for subscription services. We believe that our existing cash, cash equivalents, and marketable securities balances, together with cash generated from operations, will be sufficient to meet our working capital and capital expenditure requirements for at least the next 12 months.

Our future capital requirements will depend on many factors, including hosting costs to support the growth in our customer accounts and continued customer expansion, the timing and extent of spending to support product development efforts, the expansion of sales and marketing activities, the introduction of new and enhanced products, features, and functionality, and costs related to building out our leased office facilities. We may in the future enter into arrangements to acquire or invest in complementary businesses, services, and technologies, and intellectual property rights. We may be required to seek additional equity or debt financing in order to meet these future capital requirements. In the event that additional financing is required from outside sources, we may not be able to raise it on terms acceptable to us, or at all. If we are unable to raise additional capital when desired, our business, results of operations, and financial condition would be adversely affected.

Operating Activities

Our largest source of operating cash inflows is cash collections from our customers. Our primary uses of cash from operating activities are for employee-related expenditures, marketing programs, hosting costs, and rent for office space.

Net cash provided by operating activities in 2017 was $42.1 million, reflecting our net loss of $110.6 million, adjusted by non-cash charges including share-based compensation expense of $85.0 million, depreciation and amortization expense of $31.9 million, and net changes in operating assets and liabilities of $35.2 million. The net changes in operating assets and liabilities were primarily attributable to an increase in deferred revenue of $51.2 million due to sales growth and the timing of customer billings, and an increase in accrued liabilities, including accrued compensation of $14.3 million due to overall growth in our business and timing of payments. These sources of cash were offset by an increase in accounts receivable of $21.2 million due to sales growth and the timing of customer billings and collections. Other uses of cash included an increase in prepaid expenses and other current assets of $5.1 million.

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Net cash provided by operating activities in 2016 was $24.5 million, reflecting our net loss of $103.8 million, adjusted by non-cash charges including share-based compensation expense of $73.8 million, depreciation and amortization expense of $27.5 million, and net changes in operating assets and liabilities of $24.3 million. The changes in operating assets and liabilities were primarily attributable to an increase in deferred revenue of $38.4 million due to sales growth and the timing of customer billings, and an increase in accrued liabilities, including accrued compensation of $11.3 million due to overall growth in our business and timing of payments. These sources of cash were offset by an increase in accounts receivable of $11.8 million due to sales growth and the timing of customer billings and collections. Other uses of cash included an increase in prepaid expenses and other current assets of $6.3 million.

Net cash provided by operating activities in 2015 was $5.3 million, reflecting our net loss of $84.1 million, adjusted by non-cash charges including share-based compensation expense of $52.6 million, depreciation and amortization expense of $19.7 million, and changes in operating assets and liabilities. The changes in operating assets and liabilities were primarily attributable to an increase in deferred revenue of $33.9 million due to sales growth and the timing of customer billings, and an increase in accrued liabilities and accounts payable, including accrued compensation of $5.9 million due to overall growth in our business and timing of payments. These sources of cash were partially offset by an increase in accounts receivable of $15.0 million due to sales growth and the timing of customer billings and collections, and an increase in prepaid expenses and other current assets of $8.7 million.

Investing Activities

Net cash used in investing activities in 2017 of $69.9 million was primarily attributable to purchases of marketable securities of $29.5 million, net of sales and maturities, cash paid for the acquisition of Outbound Solutions, Inc., or Outbound, net of cash acquired, of $16.5 million, purchases of property and equipment of $16.4 million primarily associated with leasehold improvements for newly leased office facilities and hosting equipment to maintain our self-managed colocation data centers, and capitalized internal-use software costs of $7.5 million related to the development of additional features and functionality for our products.

Net cash used in investing activities in 2016 of $182.4 million was primarily attributable to purchases of marketable securities of $155.4 million, net of sales and maturities, purchases of property and equipment of $20.6 million primarily associated with leasehold improvements for newly leased office facilities and hosting equipment to maintain our self-managed colocation data centers, and capitalized internal-use software costs of $6.3 million related to the development of additional features and functionality for our products.

Net cash used in investing activities in 2015 of $72.7 million was primarily attributable to cash paid for the acquisition of We Are Cloud SAS, or WAC, net of cash acquired, of $42.8 million, purchases of property and equipment of $23.0 million primarily associated with hosting equipment to build out our self-managed colocation data centers, capitalized internal-use software costs of $4.7 million related to the development of additional features and functionality for our products, and purchases of marketable securities of $1.2 million, net of sales and maturities.

Financing Activities

Net cash provided by financing activities in 2017 of $43.1 million was primarily attributable to proceeds from exercises of employee stock options of $31.9 million and proceeds from our employee stock purchase plan of $14.2 million.

Net cash provided by financing activities in 2016 of $35.6 million was primarily attributable to proceeds from exercises of employee stock options of $25.4 million and proceeds from our employee stock purchase plan of $11.0 million.

Net cash provided by financing activities in 2015 of $203.1 million was primarily attributable to net proceeds from the follow-on public offering of our common stock of $190.1 million, proceeds from exercises of employee stock options of $10.6 million, and proceeds from our employee stock purchase plan of $9.5 million. Cash provided by financing activities was partially offset by repayment of the outstanding balance under our credit facility of $7.0 million in connection with our termination of the credit facility.

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Contractual Obligations and Other Commitments

Our principal commitments consist of obligations under our operating leases for office space, and contractual commitments for hosting and other support services. The following table summarizes our contractual obligations as of December 31, 2017 (in thousands):