commercial vehicles, engines, and power systems; and the return realized from our investments in various joint ventures and other non-consolidated investments. See “Forward-Looking Statements” below.
Critical Accounting Policies and Estimates
The preparation of financial statements in accordance with accounting principles generally accepted in the United States of America requires the application of accounting policies that often involve making estimates and employing judgments. Such judgments influence the assets, liabilities, revenues and expenses recognized in our financial statements. Management, on an ongoing basis, reviews these estimates and assumptions. Management may determine that modifications in assumptions and estimates are required, which may result in a material change in our results of operations or financial position.
The following are the accounting policies applied in the preparation of our financial statements that management believes are most dependent upon the use of estimates and assumptions.
Dealership Vehicle, Parts and Service Sales. We record revenue when vehicles are delivered and title and risks of ownership have passed to the customer, when vehicle service or repair work is completed, and when parts are delivered to our customers. Sales promotions that we offer to customers are accounted for as a reduction of revenues at the time of sale. Rebates and other incentives offered directly to us by manufacturers are recognized as a reduction of cost of sales. Reimbursements of qualified advertising expenses are treated as a reduction of selling, general and administrative expenses. The amounts received under certain manufacturer rebate and incentive programs are based on the attainment of program objectives, and such earnings are recognized either upon the sale of the vehicle for which the award was received, or upon attainment of the particular program goals if not associated with individual vehicles. Taxes collected from customers and remitted to governmental authorities are recorded on a net basis (excluded from revenue). During the nine months ended September 30, 2017 and 2016, we earned $506.9 million and $475.6 million, respectively, of rebates, incentives and reimbursements from manufacturers, of which $493.5 million and $463.7 million, respectively, were recorded as a reduction of cost of sales. The remaining $13.4 million and $11.9 million, respectively, were recorded as a reduction of selling, general and administrative expenses.
Dealership Finance and Insurance Sales. Subsequent to the sale of a vehicle to a customer, we sell installment sale contracts to various financial institutions on a non-recourse basis (with specified exceptions) to mitigate the risk of default. We receive a commission from the lender equal to either the difference between the interest rate charged to the customer and the interest rate set by the financing institution or a flat fee. We also receive commissions for facilitating the sale of various products to customers, including guaranteed vehicle protection insurance, vehicle theft protection and extended service contracts. These commissions are recorded as revenue at the time the customer enters into the contract. In the case of finance contracts, a customer may prepay or fail to pay their contract, thereby terminating the contract. Customers may also terminate extended service contracts and other insurance products, which are fully paid at purchase, and become eligible for refunds of unused premiums. In these circumstances, a portion of the commissions we received may be charged back based on the terms of the contracts. The revenue we record relating to these transactions is net of an estimate of the amount of chargebacks we will be required to pay. Our estimate is based upon our historical experience with similar contracts, including the impact of refinance and default rates on retail finance contracts and cancellation rates on extended service contracts and other insurance products. Aggregate reserves relating to chargeback activity were $25.0 million and $23.5 million as of September 30, 2017 and December 31, 2016, respectively.
Commercial Vehicle Distribution. Revenue from the distribution of vehicles, engines, power systems and parts is recognized at the time of delivery of goods to the retailer or the ultimate customer.
Other indefinite-lived intangible assets are assessed for impairment annually on October 1 and upon the occurrence of an indicator of impairment through a comparison of its carrying amount and estimated fair value. An indicator of impairment exists if the carrying value exceeds its estimated fair value and an impairment loss may be recognized up to