Revenue Recognition and Deferred Revenue Product sales and rentals The majority of our revenue relates to the sales of products through our bookstore locations, including virtual bookstores, and our bookstore affiliated ecommerce websites, and contains a single performance obligation. Revenue from sales of our products is recognized at the point in time when control of the products is transferred to our customers in an amount that reflects the consideration we expect to be entitled to in exchange for the products. For additional information, see Part II - Item 8. Financial Statements and Supplementary Data - Note 4. Revenue. Retail product revenue is recognized when the customer takes physical possession of our products, which occurs either at the point of sale for products purchased at physical locations or upon receipt of our products by our customers for products ordered through our websites and virtual bookstores. Wholesale product revenue is recognized upon shipment of physical textbooks at which point title passes and risk of loss is transferred to the customer. Additional revenue is recognized for shipping charges billed to customers and shipping costs are accounted for as fulfillment costs within cost of goods sold. Revenue from the rental of physical textbooks, which contains a single performance obligation, is deferred and recognized over the rental period based on the passage of time commencing at the point of sale, when control of the product transfers to the customer. Rental periods are typically for a single semester and are always less than one year in duration. We offer a buyout option to allow the purchase of a rented physical textbook at the end of the rental period if the customer desires to do so. We record the buyout purchase when the customer exercises and pays the buyout option price which is determined at the time of the buyout. In these instances, we accelerate any remaining deferred rental revenue at the point of sale. Revenue from the rental of digital textbooks, which contains a single performance obligation, is recognized at the point of sale. A software feature is embedded within the content of our digital textbooks, such that upon expiration of the rental term the customer is no longer able to access the content. While the digital rental allows the customer to access digital content for a fixed period of time, once the digital content is delivered to the customer, our performance obligation is complete. We estimate returns based on an analysis of historical experience. A provision for anticipated merchandise returns is provided through a reduction of sales and cost of goods sold in the period that the related sales are recorded. For sales and rentals involving third-party products, we evaluate whether we are acting as a principal or an agent. Our determination is based on our evaluation of whether we control the specified goods or services prior to transferring them to the customer. There are significant judgments involved in determining whether we control the specified goods or services prior to transferring them to the customer including whether we have the ability to direct the use of the good or service and obtain substantially all of the remaining benefits from the good or service. For those transactions where we are the principal, we record revenue on a gross basis, and for those transactions where we are an agent to a third-party, we record revenue on a net basis. We do not have gift card or customer loyalty programs. We do not treat any promotional offers as expenses. Sales tax collected from our customers is excluded from reported revenues. Our payment terms are generally 30 days and do not extend beyond one year. Service and other revenue Service and other revenue primarily relates to direct-to-student subscription-based writing service revenues and partnership marketing services which includes promotional activities and advertisements within our physical bookstores and web properties performed on behalf of third-party customers. Subscription-based revenue, which contains a single performance obligation, is deferred and recognized based on the passage of time over the subscription period commencing at the point of sale, when control of the service transfers to the customer. The majority of subscriptions sold are one month in duration. Partnership marketing agreements often include multiple performance obligations which are individually negotiated with our customers. For these arrangements that contain distinct performance obligations, we allocate the transaction price based on the relative standalone selling price method by comparing the standalone selling price (SSP) of each distinct performance obligation to the total value of the contract. The revenue is recognized as each performance obligation is satisfied, typically at a point in time for partnership marketing service and overtime for advertising efforts as measured based upon the passage of time for contracts that are based on a stated period of time or the number of impressions delivered for contracts with a fixed number of impressions.