DESCRIPTION OF BUSINESS AND ACCOUNTING POLICIES

Description of Business

Amazon.com opened its virtual doors on the World Wide Web in July 1995. We seek to be Earth’s most customer-centric company. In each of our segments, we serve our primary customer sets, consisting of consumers, sellers, developers, enterprises, and content creators. We serve consumers through our retail websites and physical stores and focus on selection, price, and convenience. We also manufacture and sell electronic devices. We offer programs that enable sellers to sell their products on our websites and their own branded websites and to fulfill orders through us, and programs that allow authors, musicians, filmmakers, app developers, and others to publish and sell content. We serve developers and enterprises of all sizes through our AWS segment, which offers a broad set of global compute, storage, database, and other service offerings. In addition, we provide services, such as fulfillment, publishing, certain digital content subscriptions, advertising, and co-branded credit cards.

We have organized our operations into three segments: North America, International, and AWS. See “Note 11—Segment Information.”

Prior Period Reclassifications

Certain prior period amounts have been reclassified to conform to the current period presentation, including the expanded presentation of “Net cash provided by (used in) investing activities” on our consolidated statements of cash flows and the allocation of stock-based compensation to “Other operating expense, net” in the segment results within “Note 11 - Segment Information.” These revised segment results reflect the way our chief operating decision maker evaluates the Company’s business performance and manages its operations. In addition, excess tax benefits from stock-based compensation were reclassified from “Net cash provided by (used in) financing activities” to “Net cash provided by (used in) operating activities” on our consolidated statements of cash flows as a result of the adoption of new accounting guidance.

Principles of Consolidation

The consolidated financial statements include the accounts of Amazon.com, Inc., its wholly-owned subsidiaries, and those entities in which we have a variable interest and of which we are the primary beneficiary, including certain entities in India and China and that support our seller lending financing activities (collectively, the “Company”). Intercompany balances and transactions between consolidated entities are eliminated. The financial results of Whole Foods Market, Inc. (“Whole Foods Market”) have been included in our consolidated financial statements from the date of acquisition on August 28, 2017.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires estimates and assumptions that affect the reported amounts of assets and liabilities, revenues and expenses, and related disclosures of contingent liabilities in the consolidated financial statements and accompanying notes. Estimates are used for, but not limited to, determining the selling price of products and services in multiple element revenue arrangements and determining the amortization period of these elements, incentive discount offers, sales returns, vendor funding, stock-based compensation forfeiture rates, income taxes, valuation and impairment of investments, inventory valuation and inventory purchase commitments, collectability of receivables, valuation of acquired intangibles and goodwill, depreciable lives of property and equipment, internal-use software and website development costs, acquisition purchase price allocations, investments in equity interests, and contingencies. Actual results could differ materially from those estimates.

Earnings per Share

Basic earnings per share is calculated using our weighted-average outstanding common shares. Diluted earnings per share is calculated using our weighted-average outstanding common shares including the dilutive effect of stock awards as determined under the treasury stock method. In periods when we have a net loss, stock awards are excluded from our calculation of earnings per share as their inclusion would have an antidilutive effect.

The following table shows the calculation of diluted shares (in millions):



	Year Ended December 31,
	2015	2016	2017
Shares used in computation of basic earnings per share	467	474	480
Total dilutive effect of outstanding stock awards	10	10	13
Shares used in computation of diluted earnings per share	477	484	493

Revenue

We recognize revenue from product sales or services rendered when the following four criteria are met: persuasive evidence of an arrangement exists, delivery has occurred or service has been rendered, the selling price is fixed or determinable, and collectability is reasonably assured. Revenue arrangements with multiple deliverables are divided into separate units and revenue is allocated using estimated selling prices if we do not have vendor-specific objective evidence or third-party evidence of the selling prices of the deliverables. We allocate the arrangement price to each of the elements based on the relative selling prices of each element. Estimated selling prices are management’s best estimates of the prices that we would charge our customers if we were to sell the standalone elements separately and include considerations of customer demand, prices charged by us and others for similar deliverables, and the price if largely based on the cost of producing the product or service.

Sales of certain of our digital devices are considered arrangements with multiple deliverables, consisting of the device, undelivered software upgrades and/or undelivered non-software services such as cloud services. The revenue allocated to the device, which is the substantial portion of the total sale price, and related costs are generally recognized upon delivery. Revenue related to undelivered software upgrades and/or undelivered non-software services is deferred and recognized generally on a straight-line basis over the estimated period the software upgrades and non-software services are expected to be provided for each of these devices.

Sales of Amazon Prime memberships are also considered arrangements with multiple deliverables, including shipping benefits, Prime Video, Prime Music, Prime Photos, and access to the Kindle Owners’ Lending Library. The revenue related to the deliverables is amortized over the life of the membership based on the estimated delivery of services. Amazon Prime membership fees are allocated between product sales and service sales. Costs to deliver Amazon Prime benefits are recognized as cost of sales as incurred. As we add more benefits to the Prime membership, we update the method of determining the estimated selling prices of each element as well as the allocation of Prime membership fees.

We evaluate whether it is appropriate to record the gross amount of product sales and related costs or the net amount earned as commissions. Generally, when we are primarily obligated in a transaction, are subject to inventory risk, have latitude in establishing prices and selecting suppliers, or have several but not all of these indicators, revenue is recorded at the gross sale price. We generally record the net amounts as commissions earned if we are not primarily obligated and do not have latitude in establishing prices. Such amounts earned are determined using fixed fees, a percentage of seller revenues, per-unit activity fees, or some combination thereof.

Product sales represent revenue from the sale of products and related shipping fees and digital media content where we record revenue gross. Product sales and shipping revenues, net of promotional discounts, rebates, and return allowances, are recorded when the products are shipped and title passes to customers. Retail sales to customers are made pursuant to a sales contract that provides for transfer of both title and risk of loss upon our delivery to the carrier or the customer. Amazon’s electronic devices sold through retailers are recognized at the point of sale to consumers.

Service sales represent third-party seller fees earned (including commissions) and related shipping fees, AWS sales, certain digital content subscriptions, certain advertising services, and our co-branded credit card agreements. Service sales, net of promotional discounts and return allowances, are recognized when service has been rendered.

Return allowances, which reduce revenue and cost of sales, are estimated using historical experience. Allowance for returns was $153 million, $156 million, and $62 million as of December 31, 2015, 2016, and 2017. Additions to the allowance were $1.3 billion, $1.5 billion, and $1.8 billion, and deductions to the allowance were $1.3 billion, $1.5 billion, and $1.9 billion in 2015, 2016, and 2017. Revenue from product sales and services rendered is recorded net of sales and consumption taxes. Additionally, we periodically provide incentive offers to our customers to encourage purchases. Such offers include current discount offers, such as percentage discounts off current purchases, inducement offers, such as offers for future discounts subject to a minimum current purchase, and other similar offers. Current discount offers, when accepted by our customers, are treated as a reduction to the purchase price of the related transaction, while inducement offers, when accepted by our customers, are treated as a reduction to purchase price based on estimated future redemption rates. Redemption rates are estimated using our historical experience for similar inducement offers. Current discount offers and inducement offers are presented as a net amount in “Total net sales.”

Cost of Sales

Cost of sales primarily consists of the purchase price of consumer products, digital media content costs where we record revenue gross, including video and music, packaging supplies, sortation and delivery centers and related equipment costs, and inbound and outbound shipping costs, including where we are the transportation service provider. Shipping costs to receive products from our suppliers are included in our inventory, and recognized as cost of sales upon sale of products to our customers. Payment processing and related transaction costs, including those associated with seller transactions, are classified in “Fulfillment” on our consolidated statements of operations.

Vendor Agreements

We have agreements with our vendors to receive funds for advertising services, cooperative marketing efforts, promotions, and volume rebates. We generally consider amounts received from vendors to be a reduction of the prices we pay for their goods, including property and equipment, or services, and therefore record those amounts as a reduction of the cost of inventory, cost of services, or cost of property and equipment. Vendor rebates are typically dependent upon reaching minimum purchase thresholds. We evaluate the likelihood of reaching purchase thresholds using past experience and current year forecasts. When volume rebates can be reasonably estimated, we record a portion of the rebate as we make progress towards the purchase threshold.

When we receive direct reimbursements for costs incurred by us in advertising the vendor’s product or service, the amount we receive is recorded as an offset to “Marketing” on our consolidated statements of operations.

Fulfillment

Fulfillment costs primarily consist of those costs incurred in operating and staffing our North America and International segments’ fulfillment centers, customer service centers, and physical stores, including costs attributable to buying, receiving, inspecting, and warehousing inventories; picking, packaging, and preparing customer orders for shipment; payment processing and related transaction costs, including costs associated with our guarantee for certain seller transactions; responding to inquiries from customers; and supply chain management for our manufactured electronic devices. Fulfillment costs also include amounts paid to third parties that assist us in fulfillment and customer service operations.

Marketing

Marketing costs primarily consist of targeted online advertising, payroll and related expenses for personnel engaged in marketing and selling activities, and television advertising. We pay commissions to participants in our Associates program when their customer referrals result in product sales and classify such costs as “Marketing” on our consolidated statements of operations. We also participate in cooperative advertising arrangements with certain of our vendors, and other third parties.

Advertising and other promotional costs are expensed as incurred and were $3.8 billion, $5.0 billion, and $6.3 billion in 2015, 2016, and 2017. Prepaid advertising costs were not significant as of December 31, 2016 and 2017.

Technology and Content

Technology and content costs include payroll and related expenses for employees involved in the research and development of new and existing products and services, development, design, and maintenance of our websites, curation and display of products and services made available on our websites, and infrastructure costs. Infrastructure costs include servers, networking equipment, and data center related depreciation, rent, utilities, and other expenses necessary to support AWS, as well as these and other efforts. Collectively, these costs reflect the investments we make in order to offer a wide variety of products and services to our customers.

Technology and content costs are expensed as incurred, except for certain costs relating to the development of internal-use software and website development costs, including software used to upgrade and enhance our websites and applications supporting our business, which are capitalized and amortized over two years.

General and Administrative

General and administrative expenses primarily consist of payroll and related expenses; facilities and equipment, such as depreciation expense and rent; professional fees and litigation costs; and other general corporate costs for corporate functions, including accounting, finance, tax, legal, and human resources, among others.

Stock-Based Compensation

Compensation cost for all stock awards expected to vest is measured at fair value on the date of grant and recognized over the service period. The fair value of restricted stock units is determined based on the number of shares granted and the quoted price of our common stock, and the fair value of stock options is estimated on the date of grant using the Black-Scholes model. Such value is recognized as expense over the service period, net of estimated forfeitures, using the accelerated method. The estimated number of stock awards that will ultimately vest requires judgment, and to the extent actual results or updated estimates differ from our current estimates, such amounts will be recorded as a cumulative adjustment in the period estimates are revised. We consider many factors when estimating expected forfeitures, including employee level, economic conditions, time remaining to vest, and historical forfeiture experience.

Other Operating Expense, Net

Other operating expense, net, consists primarily of marketing-related, contract-based, and customer-related intangible asset amortization expense, and expenses related to legal settlements.

Other Income (Expense), Net

Other income (expense), net, consists primarily of foreign currency gains (losses) of $(266) million, $21 million, and $247 million in 2015, 2016, and 2017, equity warrant valuation gains (losses) of $0 million, $67 million, and $109 million in 2015, 2016, and 2017, and realized gains (losses) on marketable securities sales of $(5) million, $(8) million, and $(7) million in 2015, 2016, and 2017.

Income Taxes

Income tax expense includes U.S. (federal and state) and foreign income taxes. Tax legislation commonly known as the Tax Cuts and Jobs Act of 2017 (the “2017 Tax Act”) includes a mandatory one-time tax on accumulated earnings of foreign subsidiaries, and as a result, all previously unremitted earnings for which no U.S. deferred tax liability had been accrued have now been subject to U.S. tax. Notwithstanding the U.S. taxation of these amounts, we intend to continue to invest most or all of these earnings, as well as our capital in these subsidiaries, indefinitely outside of the U.S. and do not expect to incur any significant, additional taxes related to such amounts.

Deferred income tax balances reflect the effects of temporary differences between the carrying amounts of assets and liabilities and their tax bases and are stated at enacted tax rates expected to be in effect when taxes are actually paid or recovered.

Deferred tax assets are evaluated for future realization and reduced by a valuation allowance to the extent we believe they will not be realized. We consider many factors when assessing the likelihood of future realization of our deferred tax assets, including our recent cumulative loss experience and expectations of future earnings, capital gains and investment in such jurisdiction, the carry-forward periods available to us for tax reporting purposes, and other relevant factors.

We utilize a two-step approach to recognizing and measuring uncertain income tax positions (tax contingencies). The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates it is more likely than not that the position will be sustained on audit, including resolution of related appeals or litigation processes. The second step is to measure the tax benefit as the largest amount which is more than 50% likely of being realized upon ultimate settlement. We consider many factors when evaluating our tax positions and estimating our tax benefits, which may require periodic adjustments and which may not accurately forecast actual outcomes. We include interest and penalties related to our tax contingencies in income tax expense.

Fair Value of Financial Instruments

Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. To increase the comparability of fair value measures, the following hierarchy prioritizes the inputs to valuation methodologies used to measure fair value:

Level 1—Valuations based on quoted prices for identical assets and liabilities in active markets.

Level 2—Valuations based on observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets and liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data.

Level 3—Valuations based on unobservable inputs reflecting our own assumptions, consistent with reasonably available assumptions made by other market participants. These valuations require significant judgment.

For our cash, cash equivalents, or marketable securities, we measure the fair value of money market funds and equity securities based on quoted prices in active markets for identical assets or liabilities. All other financial instruments were valued either based on recent trades of securities in inactive markets or based on quoted market prices of similar instruments and other significant inputs derived from or corroborated by observable market data. We did not hold any cash, cash equivalents, or marketable securities categorized as Level 3 assets as of December 31, 2016 and 2017.

As part of entering into commercial agreements, we often obtain equity warrant assets giving us the right to acquire stock of other companies. As of December 31, 2016 and 2017, these warrants had a fair value of $223 million and $441 million, and are recorded within “Other assets” on our consolidated balance sheets. The related gain (loss) recorded in “Other income (expense), net” was $0 million, $67 million, and $109 million in 2015, 2016, and 2017. These assets are primarily classified as Level 2 assets.

Cash and Cash Equivalents

We classify all highly liquid instruments with an original maturity of three months or less as cash equivalents.

Inventories

Inventories, consisting of products available for sale, are primarily accounted for using the first-in, first-out method, and are valued at the lower of cost and net realizable value. This valuation requires us to make judgments, based on currently available information, about the likely method of disposition, such as through sales to individual customers, returns to product vendors, or liquidations, and expected recoverable values of each disposition category.

We provide Fulfillment by Amazon services in connection with certain of our sellers’ programs. Third-party sellers maintain ownership of their inventory, regardless of whether fulfillment is provided by us or the third-party sellers, and therefore these products are not included in our inventories.

We also purchase electronic device components from a variety of suppliers and use several contract manufacturers to provide manufacturing services for our products. During the normal course of business, in order to manage manufacturing lead times and help ensure adequate supply, we enter into agreements with contract manufacturers and suppliers for certain electronic device components. A portion of our reported purchase commitments arising from these agreements consists of firm, non-cancellable commitments. These commitments are based on forecasted customer demand. If we reduce these commitments, we may incur additional costs. We also have firm, non-cancellable commitments for certain products offered in our Whole Foods Market stores.

Accounts Receivable, Net and Other

Included in “Accounts receivable, net and other” on our consolidated balance sheets are amounts primarily related to customers, sellers, and vendors. As of December 31, 2016 and 2017, customer receivables, net, were $3.9 billion and $6.4 billion, seller receivables, net, were $661 million and $692 million, and vendor receivables, net, were $2.0 billion and $2.6 billion. Seller receivables are amounts due from sellers related to our seller lending program, which provides funding to sellers primarily to procure inventory.

We estimate losses on receivables based on known troubled accounts and historical experience of losses incurred. Receivables are considered impaired and written-off when it is probable that all contractual payments due will not be collected in accordance with the terms of the agreement. The allowance for doubtful accounts was $189 million, $237 million, and $348 million as of December 31, 2015, 2016, and 2017. Additions to the allowance were $289 million, $451 million, and $626 million, and deductions to the allowance were $290 million, $403 million, and $515 million in 2015, 2016, and 2017. The allowance for loan losses related to our seller receivables was not material as of December 31, 2016 and 2017.

Internal-Use Software and Website Development

Costs incurred to develop software for internal use and our websites are capitalized and amortized over the estimated useful life of the software. Costs related to design or maintenance of internal-use software and website development are expensed as incurred. For the years ended 2015, 2016, and 2017, we capitalized $642 million (including $114 million of stock-based compensation), $511 million (including $94 million of stock-based compensation), and $395 million (including $84 million of stock-based compensation) of costs associated with internal-use software and website development. Amortization of previously capitalized amounts was $635 million, $634 million, and $545 million for 2015, 2016, and 2017.

Property and Equipment, Net

Property and equipment are stated at cost less accumulated depreciation. Incentives that we receive from property and equipment vendors are recorded as a reduction in our costs. Property includes buildings and land that we own, along with property we have acquired under build-to-suit, finance, and capital lease arrangements. Equipment includes assets such as furniture and fixtures, heavy equipment, servers and networking equipment, and internal-use software and website development. Depreciation is recorded on a straight-line basis over the estimated useful lives of the assets (generally the lesser of 40 years or the remaining life of the underlying building, two years for assets such as internal-use software, three years for our servers, five years for networking equipment, five years for furniture and fixtures, and ten years for heavy equipment). Depreciation expense is classified within the corresponding operating expense categories on our consolidated statements of operations.

Leases and Asset Retirement Obligations

We categorize leases at their inception as either operating or capital leases. On certain of our lease agreements, we may receive rent holidays and other incentives. We recognize lease costs on a straight-line basis without regard to deferred payment terms, such as rent holidays, that defer the commencement date of required payments. Additionally, incentives we receive are treated as a reduction of our costs over the term of the agreement. Leasehold improvements are capitalized at cost and amortized over the lesser of their expected useful life or the non-cancellable term of the lease.

We establish assets and liabilities for the estimated construction costs incurred under build-to-suit lease arrangements to the extent we are involved in the construction of structural improvements or take construction risk prior to commencement of a lease. Upon occupancy of facilities under build-to-suit leases, we assess whether these arrangements qualify for sales recognition under the sale-leaseback accounting guidance. If we continue to be the deemed owner, the facilities are accounted for as finance leases.

We establish assets and liabilities for the present value of estimated future costs to retire long-lived assets at the termination or expiration of a lease. Such assets are depreciated over the lease period into operating expense, and the recorded liabilities are accreted to the future value of the estimated retirement costs.

Goodwill

We evaluate goodwill for impairment annually or more frequently when an event occurs or circumstances change that indicate the carrying value may not be recoverable. In testing goodwill for impairment, we may elect to utilize a qualitative assessment to evaluate whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If our qualitative assessment indicates that goodwill impairment is more likely than not, we perform a two-step impairment test. We test goodwill for impairment under the two-step impairment test by first comparing the book value of net assets to the fair value of the reporting units. If the fair value is determined to be less than the book value or qualitative factors indicate that it is more likely than not that goodwill is impaired, a second step is performed to compute the amount of impairment as the difference between the estimated fair value of goodwill and the carrying value. We estimate the fair value of the reporting units using discounted cash flows. Forecasts of future cash flows are based on our best estimate of future net sales and operating expenses, based primarily on expected category expansion, pricing, market segment share, and general economic conditions.

We completed the required annual testing of goodwill for impairment for all reporting units as of April 1, 2017, and determined that goodwill is not impaired as the fair value of our reporting units substantially exceeded their book value. There were no triggering events identified from the date of our assessment through December 31, 2017 that would require an update to our annual impairment test. See “Note 4—Acquisitions, Goodwill, and Acquired Intangible Assets.”

Other Assets

Included in “Other assets” on our consolidated balance sheets are amounts primarily related to acquired intangible assets, net of amortization; video and music content, net of amortization; long-term deferred tax assets; certain equity investments; marketable securities restricted for longer than one year, the majority of which are attributable to collateralization of bank guarantees and debt related to our international operations; and equity warrant assets.

Video and Music Content

We obtain video and music content for customers through licensing agreements that have a wide range of licensing provisions, which include both fixed and variable payment schedules. When the license fee for a specific movie, television, or music title is determinable or reasonably estimable and the content is available for streaming, we recognize an asset representing the fee and a corresponding liability for the amounts owed. We relieve the liability as payments are made and we amortize the asset to “Cost of sales” on a straight-line basis or on an accelerated basis, based on estimated usage patterns, which typically ranges from one to five years. If we are unable to reasonably estimate the cost per title, no asset or liability is recorded and licensing costs are expensed as incurred. We also develop original content. Capitalized production costs associated with our original content are limited by the amount of revenue we expect to earn, which results in a portion being expensed as incurred. These capitalized costs are amortized to “Cost of sales” on an accelerated basis that follows the viewing pattern of customer streams in the first months after availability.

Investments

We generally invest our excess cash in investment grade short- to intermediate-term fixed income securities and AAA-rated money market funds. Such investments are included in “Cash and cash equivalents” or “Marketable securities” on the accompanying consolidated balance sheets. Marketable securities are classified as available-for-sale and reported at fair value with unrealized gains and losses included in “Accumulated other comprehensive loss.”

Equity investments are accounted for using the equity method of accounting if the investment gives us the ability to exercise significant influence, but not control, over an investee. Equity-method investments are included within “Other assets” on our consolidated balance sheets. Our share of the earnings or losses as reported by equity-method investees, amortization of basis differences, and related gains or losses, if any, are classified as “Equity-method investment activity, net of tax” on our consolidated statements of operations.

Equity investments without readily determinable fair values and for which we do not have the ability to exercise significant influence are accounted for using the cost method of accounting and classified as “Other assets” on our consolidated balance sheets. Under the cost method, investments are carried at cost and are adjusted only for other-than-temporary declines in fair value, certain distributions, and additional investments.

Equity investments that have readily determinable fair values are classified as available-for-sale and are included in “Marketable securities” on our consolidated balance sheets and are recorded at fair value with unrealized gains and losses, net of tax, included in “Accumulated other comprehensive loss.”

We periodically evaluate whether declines in fair values of our investments below their book value are other-than-temporary. This evaluation consists of several qualitative and quantitative factors regarding the severity and duration of the unrealized loss as well as our ability and intent to hold the investment until a forecasted recovery occurs. Additionally, we assess whether we have plans to sell the security or it is more likely than not we will be required to sell any investment before recovery of its amortized cost basis. Factors considered include quoted market prices; recent financial results and operating trends; implied values from any recent transactions or offers of investee securities; credit quality of debt instrument issuers; other publicly available information that may affect the value of our investments; duration and severity of the decline in value; and our strategy and intentions for holding the investment.

Long-Lived Assets

Long-lived assets, other than goodwill, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets might not be recoverable. Conditions that would necessitate an impairment assessment include a significant decline in the observable market value of an asset, a significant change in the extent or manner in which an asset is used, or any other significant adverse change that would indicate that the carrying amount of an asset or group of assets may not be recoverable.

For long-lived assets used in operations, impairment losses are only recorded if the asset’s carrying amount is not recoverable through its undiscounted, probability-weighted future cash flows. We measure the impairment loss based on the difference between the carrying amount and estimated fair value. Long-lived assets are considered held for sale when certain criteria are met, including when management has committed to a plan to sell the asset, the asset is available for sale in its immediate condition, and the sale is probable within one year of the reporting date. Assets held for sale are reported at the lower of cost or fair value less costs to sell. Assets held for sale were not significant as of December 31, 2016 and 2017.

Accrued Expenses and Other

Included in “Accrued expenses and other” on our consolidated balance sheets are liabilities primarily related to unredeemed gift cards, leases and asset retirement obligations, current debt, acquired digital media content, and other operating expenses.

As of December 31, 2016 and 2017, our liabilities for unredeemed gift cards was $2.4 billion and $3.0 billion. We reduce the liability for a gift card when redeemed by a customer. If a gift card is not redeemed, we recognize revenue when it expires or when the likelihood of its redemption becomes remote, generally two years from the date of issuance.

Unearned Revenue

Unearned revenue is recorded when payments are received in advance of performing our service obligations and is recognized over the service period. Unearned revenue primarily relates to prepayments of Amazon Prime memberships and AWS services. Included in “Other long-term liabilities” on our consolidated balance sheets was $499 million and $1.0 billion of unearned revenue as of December 31, 2016 and 2017. The amortization of previously unearned revenue was approximately $10.0 billion and $14.3 billion in 2016 and 2017.

Foreign Currency

We have internationally-focused websites for Australia, Brazil, Canada, China, France, Germany, India, Italy, Japan, Mexico, the Netherlands, Spain, and the United Kingdom. Net sales generated from these websites, as well as most of the related expenses directly incurred from those operations, are denominated in local functional currencies. The functional currency of our subsidiaries that either operate or support these websites is generally the same as the local currency. Assets and liabilities of these subsidiaries are translated into U.S. Dollars at period-end foreign exchange rates, and revenues and expenses are translated at average rates prevailing throughout the period. Translation adjustments are included in “Accumulated other comprehensive loss,” a separate component of stockholders’ equity, and in the “Foreign currency effect on cash and cash equivalents,” on our consolidated statements of cash flows. Transaction gains and losses including intercompany transactions denominated in a currency other than the functional currency of the entity involved are included in “Other income (expense), net” on our consolidated statements of operations. In connection with the settlement and remeasurement of intercompany balances, we recorded a loss of $215 million in 2015 and recorded gains of $62 million and $202 million in 2016 and 2017.

Accounting Pronouncements Recently Adopted

In July 2015, the Financial Accounting Standards Board (“FASB”) issued an Accounting Standards Update (“ASU”) modifying the accounting for inventory. Under this ASU, the measurement principle for inventory changed from lower of cost or market value to lower of cost and net realizable value. The ASU defines net realizable value as the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The ASU is applicable to inventory that is accounted for under the first-in, first-out method. We adopted this ASU in Q1 2017 with no material impact to our consolidated financial statements.

In March 2016, the FASB issued an ASU amending the accounting for stock-based compensation and requiring excess tax benefits and deficiencies to be recognized as a component of income tax expense rather than equity. The inclusion of excess tax benefits and deficiencies as a component of our income tax expense will increase volatility within our provision for income taxes as the amount of excess tax benefits or deficiencies from stock-based compensation awards depends on our stock price at the date the awards vest. This guidance also requires excess tax benefits to be presented as an operating activity on the statement of cash flows and allows an entity to make an accounting policy election to either estimate expected forfeitures or to account for them as they occur. We adopted this ASU in Q1 2017 by recording the cumulative impact through an increase in retained earnings of $687 million, and we will continue to estimate expected forfeitures. Additionally, we retrospectively adjusted our consolidated statements of cash flows to reclassify excess tax benefits of $119 million and $829 million for the year ended December 31, 2015 and 2016 from financing activities to operating activities.

Accounting Pronouncements Not Yet Adopted

In May 2014, the FASB issued an ASU amending revenue recognition guidance and requiring more detailed disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. We will adopt this ASU on January 1, 2018 with a cumulative adjustment that will increase retained earnings by approximately $650 million rather than retrospectively adjusting prior periods. The cumulative adjustment will primarily relate to unredeemed gift cards. We will begin to recognize revenue from estimated unredeemed gift cards over the expected customer redemption period, which is substantially within nine months, rather than waiting until gift cards expire or when the likelihood of redemption becomes remote, generally two years from the date of issuance. Other changes relate to Amazon-branded electronic devices sold through retailers, which will be recognized upon sale to the retailer rather than to end customers. We also will change how we recognize and classify Amazon Prime memberships, which are currently considered arrangements with multiple deliverables that are allocated among products sales and service sales. Upon adoption of the ASU, Amazon Prime memberships will be accounted for as a single performance obligation recognized ratably over the membership period and will be classified as service sales. Other changes that we have identified relate primarily to the presentation of revenue. Certain advertising services will be classified as revenue rather than a reduction in cost of sales, and sales of apps, in-app content, and certain digital media content will primarily be presented on a net basis.

In January 2016, the FASB issued an ASU which updates certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. Under this ASU, certain equity investments will be measured at fair value with changes recognized in net income. The ASU is effective for reporting periods beginning after December 15, 2017. We do not expect adoption of the ASU in Q1 2018 to have a material impact on our consolidated financial statements.

In February 2016, the FASB issued an ASU amending the accounting for leases. The new guidance requires the recognition of lease assets and liabilities for operating leases with terms of more than 12 months, in addition to those currently recorded, on our consolidated balance sheets. Presentation of leases within the consolidated statements of operations and consolidated statements of cash flows will be generally consistent with the current lease accounting guidance. The ASU is effective for reporting periods beginning after December 15, 2018, with early adoption permitted. We plan to adopt this ASU beginning in Q1 2019. We are currently evaluating the impact and expect the ASU will have a material impact on our consolidated financial statements, primarily to the consolidated balance sheets and related disclosures.

In October 2016, the FASB issued an ASU amending the accounting for income taxes. The new guidance requires the recognition of the income tax consequences of an intercompany asset transfer, other than transfers of inventory, when the transfer occurs. For intercompany transfers of inventory, the income tax effects will continue to be deferred until the inventory has been sold to a third party. The ASU is effective for reporting periods beginning after December 15, 2017, with early adoption permitted. We will adopt this ASU beginning in Q1 2018. We estimate the ASU will have an impact of approximately $250 million on our consolidated financial statements, including retained earnings and deferred taxes. This estimate takes into account valuation allowances that we anticipate recording against certain material deferred tax assets. Any change in our assessment of the likelihood of our ability to realize deferred tax assets will be reflected as an income tax benefit during the quarter of such change.

In November 2016, the FASB issued an ASU amending the presentation of restricted cash within the statement of cash flows. The new guidance requires that restricted cash be included within cash and cash equivalents on the statement of cash flows. The ASU is effective retrospectively for reporting periods beginning after December 15, 2017, with early adoption permitted. We will adopt this ASU beginning in Q1 2018.