We generate all of our revenue from contracts with customers. We recognize revenue when we satisfy a performance obligation by transferring control of the promised services to a customer in an amount that reflects the consideration that we expect to receive in exchange for those services. When we act as an agent in the transaction, we recognize revenue for only our commission on the arrangement. We determine revenue recognition through the following steps:

At contract inception, we assess the services promised in our contracts with customers and identify a performance obligation for each promise to transfer to the customer a service (or bundle of services) that is distinct. To identify the performance obligations, we consider all of the services promised in the contract regardless of whether they are explicitly stated or are implied by customary business practices. We have provided qualitative information about our performance obligations for our principal revenue streams discussed below. There was no significant revenue recognized in the years ended December 31, 2020, 2019 and 2018 related to performance obligations satisfied in prior periods, respectively. We have applied a practical expedient and do not disclose the value of unsatisfied performance obligations that have an original expected duration of less than one year, and we do not have any material unsatisfied performance obligations over one year. The value related to our remaining or partially satisfied performance obligations relates to subscription services that are satisfied over time or services that are recognized at a point in time, but not yet achieved. Our timing of services, invoicing and payments are discussed in more detail below and do not include a significant financing component. Our customer invoices are generally due 30 days from the time of invoicing.

We recognize an asset for the incremental costs of obtaining a contract with a customer if we expect the benefit of those costs to be longer than one year. Although the substantial majority of our contract costs have an amortization period of less than one year, we have determined contract costs arising from certain sales incentives have an amortization period in excess of one year given the high likelihood of contract renewal. Sales incentives are not paid upon renewal of these contracts and therefore are not commensurate with the initial sales incentive costs. As of both December 31, 2020 and 2019, there were $4 million of unamortized contract costs in other long-term assets on our consolidated balance sheet. We amortize these contract costs on a straight-line basis over the estimated customer life, which is based on historical customer retention rates. Amortization expense recorded to selling and marketing during both the years ended December 31, 2020 and 2019, were $1 million, and not material for the year ended December 31, 2018. We assess such assets for impairment when events or circumstances indicate that the carrying amount may not be recoverable.

The recognition of revenue may require the application of judgment related to the determination of the performance obligations, the timing of when the performance obligations are satisfied and other areas. The determination of our performance obligations does not require significant judgment given that we generally do not provide multiple services to a customer in a transaction, and the point in which control is transferred to the customer is readily determinable. In instances where we recognize revenue over time, we generally have either a subscription service that is recognized over time on a straight-line basis using the time-elapsed output method, or based on other output measures that provide a faithful depiction of the transfer of our services. When an estimate for cancellations is included in the transaction price, we base our estimate on historical cancellation rates and current trends. There have been no significant adjustments to our cancellation estimates and cancellation estimates are not significant. Taxes assessed by a government authority that are both imposed on and concurrent with a specific revenue–producing transaction, that are collected by us from a customer, are reported on a net basis, or in other words excluded from revenue on our consolidated financial statements. The application of our revenue recognition policies and a description of our principal activities, organized by segment, from which we generate our revenue, are presented below.

Tripadvisor-branded Hotels Revenue. Our largest source of Hotels, Media & Platform segment revenue is generated from click-based advertising on Tripadvisor-branded websites, which is primarily comprised of contextually-relevant booking links to our travel partners’ websites. Our click-based travel partners are predominantly OTAs and hotels. Click-based advertising is generally priced on a cost-per-click, or “CPC”, basis, with payments from travel partners determined by the number of travelers who click on a link multiplied by the CPC rate for each specific click. CPC rates are determined in a dynamic, competitive auction process, also known as hotel auction revenue, where our travel partner CPC bids for rates and availability to be listed on our site are submitted. When a CPC bid is submitted, the travel partner agrees to pay us the bid amount each time a traveler clicks on the link to that travel partner’s websites. Bids can be submitted periodically – as often as daily – on a property-by-property basis. We record click-based advertising revenue as the click occurs and traveler leads are sent to the travel partner websites as our performance obligation is fulfilled at that time. Click-based revenue is generally billed to our travel partners on a monthly basis consistent with the timing of the service.

In addition, we offer subscription-based advertising to hotels, owners of B&Bs and other specialty lodging properties. Our performance obligation is generally to enable subscribers to advertise their businesses on our website, as well as to manage and promote their website URL, email address, phone number, special offers and other information related to their business. Subscription-based advertising services are predominantly sold for a flat fee for a contracted period of time of one year or less and revenue is recognized on a straight-line basis over the period of the subscription service as efforts are expended evenly throughout the contract period. Subscription-based advertising services are generally billed at the inception of the service. When prepayments are received, we recognize deferred revenue for the amount of prepayment in excess of revenue recognized until the performance obligation is satisfied.

We also generate revenue from our cost-per-action, or “CPA” model, which consists of contextually-relevant booking links to our travel partners’ websites which are advertised on our platform. We earn a commission from our travel partners, based on a pre-determined contractual commission rate, for each traveler who clicks to and books a hotel reservation on the travel partners’ website, which results in a traveler stay. CPA revenue is billable only upon the completion of each traveler’s stay resulting from a hotel reservation. The travel partners provide the service to the travelers and we act as an agent under ASC 606 – Revenue from Contracts with Customers (“ASC 606”). Our performance obligation is complete at the time of the hotel reservation booking, and the commission earned is recognized upon booking, as we have no post-booking service obligations. We recognize this revenue net of an estimate of the impact of cancellations, which are not significant, using historical cancellation rates and current trends. Contract assets are recognized at the time of booking for commissions that are billable at the time of stay. To a lesser extent, we offer travel partners the opportunity to advertise and promote their business through hotel sponsored placements on our websites. This service is generally priced on a CPC basis, with payments from travel partners determined by the number of travelers who click on the sponsored link multiplied by the CPC rate for each specific click. CPC rates for hotel sponsored placements that our travel partners pay are generally based on bids submitted as part of an auction by our travel partners. When a CPC bid is submitted, the travel partner agrees to pay us the bid amount each time a traveler clicks on a link to our travel partner’s websites. Bids can be submitted periodically – as often as daily – on a property-by-property basis. We record this click-based advertising revenue as the click occurs and traveler leads are sent to the travel partner as our performance obligation is fulfilled at that time. Hotel sponsored placements revenue is generally billed to our travel partners on a monthly basis consistent with the timing of the service.

Tripadvisor-branded Display and Platform Revenue. We offer travel partners the ability to promote their brands through display-based advertising placements on our websites across all of our segments and business units. Our display-based advertising clients are predominantly direct suppliers of hotels, airlines and cruises, as well as destination marketing organizations. We also sell display-based advertising to OTAs and other travel related businesses, as well as advertisers from non-travel categories. Display-based advertising is sold predominantly on a cost per thousand impressions, or CPM, basis. The performance obligation in our display-based advertising arrangements is to display a number of advertising impressions on our websites and we recognize revenue for impressions as they are delivered. Services are generally billed monthly. We have applied the practical expedient to measure progress toward completion, as we have the right to invoice the customer in an amount that directly

corresponds with the value to the customer of our performance to date, which is measured based on impressions delivered.

We provide information and services that allow consumers to research and book tours, activities and experiences in popular travel destinations both through Viator, our dedicated Experiences offering, and on our Tripadvisor website and mobile apps. We also power travel tours, activities and experiences booking capabilities to consumers on affiliate partner websites, including some of the world’s top airlines, hotel chains, and online and offline travel agencies. We work with local tour or travel activities/experiences operators (“the supplier”) to provide consumers the ability to book tours, activities and experiences (“the activity”) in popular destinations worldwide. We generate commissions for each booking transaction we facilitate through our online reservation system. We provide post-booking service to the customer until the time of the activity, which is the completion of the performance obligation. Revenue is recognized at the time that the activity occurs. We generally do not control the activity before the supplier provides it to our customer and therefore act as agent for nearly all of these transactions under ASC 606. We generally collect payment from the customer at the time of booking that includes both our commission revenue and the amount due to the supplier. Our commission revenue is recorded as deferred revenue until the activity occurs and revenue is recognized, and the amount due to the supplier is recorded as deferred merchant payables on our consolidated balance sheet until completion of the activity and payment is made to the supplier. To a lesser extent, we earn commissions from affiliate partners, which are third-party merchant partners who display and promote on their websites the supplier activities available on our platform to generate bookings. In these transactions, where we are not the merchant of record, we generally invoice and receive commissions directly from the third-party merchant partners. Our performance obligation is to allow the third-party merchant partners to display and promote on their website suppliers who utilize our platform and we earn a commission when consumers book and complete an activity. We do not control the service and act as an agent for these transactions under ASC 606. Our performance obligation is complete and revenue is recognized at the time of the booking, as we have no post-booking obligations. We recognize this revenue net of an estimate of the impact of cancellations, which is not material, using historical cancellation rates and current trends. Contract assets are recognized for commissions that are billable contingent upon completion of the activity.

We also provide information and services for consumers to research and book restaurant reservations in popular travel destinations through our dedicated online restaurant reservations offering, TheFork, and on our Tripadvisor-branded websites and mobile apps. We primarily generate transaction fees (or per seated diner fees) that are paid by our restaurant customers for diners seated primarily from bookings through TheFork’s online reservation system. The transaction fee is recognized as revenue after the reservation is fulfilled, or as diners are seated by our restaurant customers. We invoice restaurants monthly for transaction fees. To a lesser extent, we also generate subscription fees for subscription-based advertising to restaurants, access to certain online reservation management services, marketing analytic tools, and menu syndication services provided by TheFork and Tripadvisor. As the performance obligation is to provide restaurants with access to these services over the subscription period, subscription fee revenue is recognized over the period of the subscription service on a straight-line basis as efforts are expended evenly throughout the contract period. Subscription fees are generally billable in advance of service. When prepayments are received, we recognize deferred revenue for the amount of prepayment in excess of revenue recognized until the performance obligation is satisfied. In addition, we also offer restaurant partners the opportunity to advertise and promote their business through restaurant media advertising placements on our website. This service is generally priced on a CPC basis, with payments from restaurant partners determined by the number of consumers who click on the sponsored link multiplied by the CPC rate for each specific click. CPC rates for media advertising placements that our restaurant partners pay are based on a pre-determined contractual rate. We record this click-based advertising revenue as the click occurs and diner leads are sent to the restaurant partner as our performance obligation is fulfilled at that time. Click-based revenue is generally billed to our restaurant partners on a monthly basis consistent with the timing of the service.

We provide information and services that allow travelers to research and book vacation and short-term rental properties, including full homes, condominiums, villas, beach properties, cabins and cottages. Our Rentals offering

generates revenue primarily by offering individual property owners and managers the ability to list their properties on our websites and mobile apps thereby connecting with travelers through a free-to-list, commission-based option or, to a lesser extent, by an annual subscription-based fee structure. These properties are listed on www.flipkey.com, www.holidaylettings.co.uk, www.housetrip.com, www.niumba.com, and www.vacationhomerentals.com, and on our Tripadvisor-branded websites and mobile apps. We earn commissions associated with rental transactions through our free-to-list model from both the traveler, and the property owner or manager. We provide post-booking service to the travelers, property owners and managers until the time the rental commences, which is the time the performance obligation is completed. Revenue from transaction fees is recognized at the time that the rental commences. We act as an agent, under ASC 606, in the transactions as we do not control any properties before the property owner provides the accommodation to the traveler and do not have inventory risk. We generally collect payment from the traveler at the time of booking, representing the amount due to the property owner or manager, as well as our commission. That portion of the payment representing our commission is recorded as deferred revenue until revenue is recognized, and that portion of the payment representing the amount due to the property owner is recorded as deferred merchant payables until payment is made to the property owner after the completion of the rental. Payments for term-based subscription fees related to online advertising services for the listing of rental properties are generally due in advance. As the performance obligation is the listing service provided to the property owner or manager over the subscription period, revenue is recognized over the period of the subscription service on a straight-line basis as efforts are expended evenly throughout the contract period. We recognize deferred revenue for the amount of prepayment in excess of revenue recognized until the performance obligation is satisfied.

In addition, Other also includes revenue generated from flights, cruises, and car offerings on Tripadvisor-branded websites and its portfolio of travel media brands, which primarily includes click-based advertising and display-based advertising revenue. The performance obligations, timing of customer payments for these brands, and methods of revenue recognition are generally consistent with click-based advertising and display-based advertising revenue, as described above.

We expense costs to obtain a contract as incurred, such as sales incentives, when the amortization period would have been one year or less.

We do not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which we recognize revenue at the amount to which we have the right to invoice for services performed.

We disaggregate revenue from contracts with customers into major products/revenue sources. We have determined that disaggregating revenue into these categories achieves the disclosure objective to depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. As noted in “Note 20: Segment and Geographic Information”, our business consists of two reportable segments – (1) Hotels, Media & Platform; and (2) Experiences & Dining. Other consists of a combination of business units, and does not constitute a reportable segment.

A reconciliation of disaggregated revenue to segment revenue is also included below.

	Year ended December 31,
	2020		2019		2018
Major products/revenue sources (1):	(in millions)
Hotels, Media & Platform
Tripadvisor-branded hotels	$	292	$	779	$	848
Tripadvisor-branded display and platform		69		160		153
Total Hotels, Media & Platform		361		939		1,001

Experiences & Dining		186		456		372
Other		57		165		242
Total Revenue	$	604	$	1,560	$	1,615

The following table provides information about the opening and closing balances of accounts receivables and contract assets from contracts with customers (in millions):

	December 31, 2020		December 31, 2019
Accounts receivable	$	70	$	176
Contract assets		13		7
Total	$	83	$	183

Accounts receivable are recognized when the right to consideration becomes unconditional. Contract assets are rights to consideration in exchange for services that we have transferred to a customer when that right is conditional on something other than the passage of time, such as commission payments that are contingent upon the completion of the service by the principal in the transaction. The difference between the opening and closing balances of our contract assets primarily results from the timing difference between when we satisfy our performance obligations and the time when the principal completes the service in the transaction.

During the year ended December 31, 2020, we recorded approximately $6 million of incremental allowance for expected credit losses on accounts receivable and contract assets, when compared to the same period in 2019, primarily due to the impact of COVID-19. Actual future bad debt could differ materially from this estimate resulting from changes in our assumptions of the duration and ultimate severity of the impact of the COVID-19 pandemic.

Contract liabilities generally include payments received in advance of performance under the contract, and are realized as revenue as the performance obligation to the customer is satisfied, which we present as deferred revenue on our consolidated balance sheets. As of January 1, 2020 and 2019, we had $62 million and $63 million, respectively, recorded as deferred revenue on our consolidated balance sheets, of which $51 million and $61 million, respectively, was recognized in revenue and $11 million and $2 million was refunded due to cancellations by travelers during the years ended December 31, 2020 and 2019, respectively. The difference between the opening and closing balances of our deferred revenue primarily results from the timing differences between when we receive customer payments and the time in which we satisfy our performance obligations.

There were no significant changes in contract assets or deferred revenue during the years ended December 31, 2020 and 2019 related to business combinations, impairments, cumulative catch-ups or other material adjustments. However, to the extent the COVID-19 pandemic continues, we may incur additional significant and unanticipated cancellations by consumers related to future travel, accommodations and tour bookings, which have been reserved by travelers and recorded as deferred revenue on our consolidated balance sheet as of December 31, 2020.