The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results may differ from those estimates.

The Company provides an allowance for doubtful receivables and repossession losses after considering historical loss experience and other factors that might affect the collection of accounts receivable and the ability of customers to meet their obligations on finance contracts sold by the Company.

Inventories are stated at the lower of cost or market value. Cost is determined by specific identification of new and used commercial vehicle inventory and by the first-in, first-out method for tires, parts and accessories. An allowance is provided when it is anticipated that cost will exceed net realizable value plus a reasonable profit margin.

Property and equipment are stated at cost and depreciated over their estimated useful lives. Leasehold improvements are amortized over the useful life of the improvement, or the term of the lease, whichever is shorter. Provision for depreciation of property and equipment is calculated primarily on a straight-line basis. The Company capitalizes interest on borrowings during the active construction period of major capital projects. Capitalized interest, when incurred, is added to the cost of underlying assets and is amortized over the estimated useful life of such assets. The Company capitalized interest of approximately $43,000 related to major capital projects during 2012. The cost, accumulated depreciation and amortization and estimated useful lives are summarized as follows (in thousands):

As of December 31, 2012, the Company had $48.6 million in lease and rental vehicles under various capital leases included in property and equipment, net of accumulated amortization of $20.2 million. The Company recorded depreciation expense of $62.3 million and amortization expense of $11.0 million for the year ended December 31, 2012, and depreciation expense of $48.3 million and amortization expense of $8.6 million for the year ended December 31, 2011. Depreciation and amortization of vehicles related to lease and rental operations is included in lease and rental cost of products sold.

Goodwill is the excess of the purchase price over the fair value of identifiable net assets acquired in business combinations accounted for under the purchase method. The Company does not amortize goodwill, but tests goodwill for impairment annually in the fourth quarter, or when indications of potential impairment exist. These indicators would include a significant change in operating performance, or a planned sale or disposition of a significant portion of the business, among other factors. The Company tests for goodwill impairment utilizing a fair value approach at the reporting unit level. A reporting unit is an operating segment, for which discrete financial information is prepared and regularly reviewed by segment management. The Company has deemed its reporting unit to be the Truck Segment, which is the level at which management regularly reviews operating results and makes resource allocation decisions.

The impairment test for goodwill involves comparing the fair value of a reporting unit to its carrying amount, including goodwill. If the carrying amount of the reporting unit exceeds its fair value, a second step is required to measure the goodwill impairment loss. The second step includes hypothetically valuing all the tangible and intangible assets of the reporting unit as if the reporting unit had been acquired in a business combination. Then, the implied fair value of the reporting unit's goodwill is compared to the carrying amount of that goodwill. If the carrying amount of the reporting unit's goodwill exceeds the implied fair value of the goodwill, the Company would recognize an impairment loss in an amount equal to the excess, not to exceed the carrying amount. The Company determines the fair values calculated in an impairment test using the discounted cash flow method, which requires assumptions and estimates regarding future revenue, expenses and cash flow projections. The analysis is based upon available information regarding expected future cash flows of its reporting unit discounted at rates consistent with the cost of capital specific to the reporting unit.

On December 5, 2011, the Company acquired certain assets of West Texas Peterbilt, which consisted of dealerships in Amarillo, Lubbock and Odessa, Texas that offer Peterbilt trucks, parts, service, financing and insurance, a parts and service facility in Dalhart, Texas and a parts facility in Hereford, Texas. The final purchase price allocation includes an adjustment to goodwill of $1.7 million due to the finalization of the franchise rights valuation during the second quarter of 2012.

The total capitalized costs of the SAP enterprise software and SAP dealership management system of $40.9 million, including capitalized interest, are recorded on the Consolidated Balance Sheet in Other Assets, net of accumulated amortization of $4.1 million. The SAP software will be amortized over a period of 15 years. The Company is currently operating most of its Rush Truck Centers in Texas and all of its leasing operations on the SAP enterprise software and SAP dealership management system. The Company plans to convert all of its Rush Truck Centers to the SAP enterprise software and SAP dealership management system by the end of 2014.

Amortization expense relating to intangible assets, primarily the SAP software, was $3.0 million for the year ended December 31, 2012, $1.3 million for the year ended December 31, 2011, and $0.5 million for the year ended December 31, 2010, and is recognized in depreciation and amortization expense in the Consolidated Statement of Income. The Company estimates that amortization expense relating to intangible assets will be $3.0 million for each of the next five succeeding years.

The Company’s only significant identifiable intangible assets, other than goodwill, are rights under franchise agreements with manufacturers. The fair market value of the Company’s manufacturer franchise rights, which are included in Other Assets on the accompanying consolidated balance sheets, is determined at the acquisition date through discounting the projected cash flows specific to each franchise. The Company has determined that manufacturer franchise rights have an indefinite life as there are no economic or other factors that limit their useful lives, and they are expected to generate cash flows indefinitely due to the historically long lives of the manufacturers’ brand names. Furthermore, to the extent that any agreements evidencing manufacturer franchise rights would expire, the Company expects that it would be able to renew those agreements in the ordinary course of business. Due to the fact that manufacturer franchise rights are specific to geographic region, the Company has determined that the geographic region is the appropriate level for purposes of testing franchise rights for impairment. The Company does not amortize manufacturer franchise rights.

Management reviews indefinite lived manufacturer franchise rights for impairment annually during the fourth quarter, or more often if events or circumstances indicate that impairment may have occurred. The Company is subject to financial statement risk to the extent that manufacturer franchise rights become impaired due to decreases in fair market value of its individual franchises.

The significant estimates and assumptions used by management in assessing the recoverability of manufacturer franchise rights are estimated future cash flows, present value discount rate, and other factors. Any changes in these estimates or assumptions could result in an impairment charge. The estimates of future cash flows, based on reasonable and supportable assumptions and projections, require management’s subjective judgment. Depending on the assumptions and estimates used, the estimated future cash flows projected in the evaluations of manufacturer franchise rights can vary within a range of outcomes.

Significant management judgment is required to determine the provisions for income taxes and to determine whether deferred tax assets will be realized in full or in part. Deferred income tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. When it is more likely than not that all or some portion of specific deferred income tax assets will not be realized, a valuation allowance must be established for the amount of deferred income tax assets that are determined not to be realizable. Accordingly, the facts and financial circumstances impacting state deferred income tax assets are reviewed quarterly and management’s judgment is applied to determine the amount of valuation allowance required, if any, in any given period.

In determining our provision for income taxes, the Company uses an annual effective income tax rate based on annual income, permanent differences between book and tax income, and statutory income tax rates. The effective income tax rate also reflects our assessment of the ultimate outcome of tax audits. The Company adjusts its annual effective income tax rate as additional information on outcomes or events becomes available. Discrete events such as audit settlements or changes in tax laws are recognized in the period in which they occur.

The Company’s income tax returns, like those of most companies, are periodically audited by U.S. federal, state and local tax authorities. These audits include questions regarding the Company’s tax filing positions, including the timing and amount of deductions. At any one time, multiple tax years are subject to audit by the various tax authorities. In evaluating the tax benefits associated with the Company’s various tax filing positions, it records a tax benefit for uncertain tax positions. A number of years may elapse before a particular matter, for which the Company has established a liability, is audited and effectively settled. The Company adjusts its liability for unrecognized tax benefits in the period in which it determines the issue is effectively settled with the tax authorities, the statute of limitations expires for the relevant taxing authority to examine the tax position, or when more information becomes available. The Company includes its liability for unrecognized tax benefits, including accrued interest, in accrued liabilities on the Company’s Consolidated Balance Sheet and in income tax expense in the Company’s Consolidated Statement of Income. Unfavorable settlement of any particular issue would require use of the Company’s cash and a charge to income tax expense. Favorable resolution would be recognized as a reduction to income tax expense at the time of resolution.

Additionally, despite the Company’s belief that its tax return positions are consistent with applicable tax law, management believes that certain positions may be challenged by taxing authorities. Settlement of any challenge can result in no change, a complete disallowance, or some partial adjustment reached through negotiations.

Income on the sale of a vehicle is recognized when the seller and customer execute a purchase contract, delivery has occurred and there are no significant uncertainties related to financing or collectability. Finance income related to the sale of a vehicle is recognized over the period of the respective finance contract, based on the effective interest rate method, if the finance contract is retained by the Company. During 2012, 2011 and 2010, no finance contracts were retained for any significant length of time by the Company but were generally sold, with limited recourse, to certain finance companies concurrent with the sale of the related vehicle. Finance income is recognized by the Company upon the sale of such finance contracts to the finance companies, net of a provision for estimated repossession losses and early repayment penalties. Lease and rental income is recognized over the period of the related lease or rental agreement. Contingent rental income is recognized when it is earned. Parts and services revenue is earned at the time the Company sells the parts to its customers or at the time the Company completes the service work order related to service provided to the customer’s vehicle. Payments received on prepaid maintenance plans are deferred as a component of accrued expenses and recognized as income when the maintenance is performed.

For the Company’s new and used commercial vehicle operations and its parts operations, cost of sales consists primarily of the Company’s actual purchase price, less manufacturer’s incentives, for new and used commercial vehicles and parts. The Company is subject to a chargeback of manufacturer incentives for commercial vehicles that are not sold to the customer for which they were ordered. The Company records a liability for a potential chargeback of manufacturer incentives in its financial statements. For the Company’s service and body shop operations, technician labor cost is the primary component of cost of sales. For the Company’s rental and leasing operations, cost of sales consists primarily of depreciation and amortization, rent, and interest expense on the lease and rental fleet owned and leased by the Company, and the maintenance cost of the lease and rental fleet. There are no costs of sales associated with the Company’s finance and insurance revenue or other revenue.

Selling, general and administrative expenses consist primarily of incentive based compensation for sales, finance and general management personnel, salaries for administrative personnel and expenses for rent, marketing, insurance, utilities, shipping and handling costs and other general operating purposes.

The Company applies the provisions of ASC topic 718-10, “Compensation – Stock Compensation,” which requires the measurement and recognition of compensation expense for all share-based payment awards made to employees and directors including grants of employee stock options, restricted stock units and restricted stock awards as well as employee stock purchases under the Employee Stock Purchase Plan based on estimated fair values.

Compensation expense for all share-based payment awards is recognized using the straight-line single-option method. Stock-based compensation expense recognized is based on awards ultimately expected to vest and it has been reduced for estimated forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates.

The Company’s determination of fair value of share-based payment awards on the date of grant using an option-pricing model is affected by the Company’s stock price as well as assumptions regarding a number of highly complex and subjective variables. These variables include the Company’s expected stock price volatility over the term of the awards and actual and projected stock option exercise behaviors. Option-pricing models were developed for use in estimating the value of traded options that have no vesting or hedging restrictions and are fully transferable. Because the Company’s stock options have certain characteristics that are significantly different from traded options, and because changes in the subjective assumptions can materially affect the estimated value, in management’s opinion, the existing valuation models may not provide an accurate measure of the fair value that value may not be indicative of the fair value observed in a market transaction between a willing buyer and a willing seller.

The Company computes its historical stock price volatility in accordance with ASC topic 718-10. The risk-free interest rate for periods within the contractual life of the option is based on the U.S. Treasury yield curve in effect at the time of grant. The dividend yield assumption is based on the Company’s history and expectation of dividend payouts. The expected life of stock options represents the weighted-average period the stock options are expected to remain outstanding.

The Company's accounting policy with respect to accounting for computer software developed or obtained for internal use is consistent with ASC topic 350-40 which provides guidance on accounting for the costs of computer software developed or obtained for internal use and identifies characteristics of internal-use software. The Company has capitalized software costs, including capitalized interest, of approximately $40.9 million at December 31, 2012, net of accumulated amortization of $4.1 million, and $41.9 million, net of accumulated amortization of $1.2 million at December 31, 2011.

The Company is partially self-insured for a portion of the claims related to its property and casualty insurance programs, requiring it to make estimates regarding expected losses to be incurred. The Company engages a third party administrator to assess any open claims and the Company adjusts its accrual accordingly on an annual basis. The Company is also partially self-insured for a portion of the claims related to its worker’s compensation and medical insurance programs. The Company uses actuarial information provided from third party administrators to calculate an accrual for claims incurred, but not reported, and for the remaining portion of claims that have been reported.

The Company utilizes derivative financial instruments to manage its interest rate risk. The types of risks hedged are those relating to the variability of cash flows and changes in the fair value of the Company’s financial instruments caused by movements in interest rates. The Company assesses hedge effectiveness at the inception and during the term of each hedge. Derivatives are reported at fair value on the accompanying Consolidated Balance Sheets.

At December 31, 2012, the Company had an aggregate $41.7 million notional amount of interest rate swap contracts, which have been designated as cash flow hedges, to pay fixed rates of interest and receive a floating interest rate based on LIBOR. The fixed interest rates specified in the interest rate swap contracts became effective on or about January 1, 2012.

The Company has various financial instruments that it must measure at fair value on a recurring basis, including certain available for sale securities and derivatives. See Note 9 – Financial Instruments and Fair Value of the Notes to Consolidated Financial Statements, for further information. The Company also applies the provisions of fair value measurement to various nonrecurring measurements for its financial and nonfinancial assets and liabilities.

Applicable accounting standards define fair value 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 (an exit price). The Company measures its assets and liabilities using inputs from the following three levels of the fair value hierarchy:

Level 2 inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (i.e., interest rates, yield curves, etc.), and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs).

In June 2011, the Financial Accounting Standards Board (“FASB”) issued an amendment to the existing guidance on the presentation of comprehensive income. Under the amended guidance, entities have the option to present the components of net income and other comprehensive income in either a single continuous statement of comprehensive income or in two separate but consecutive statements. Entities no longer have the option of presenting the components of other comprehensive income within the statement of changes in stockholders’ equity. This amendment was effective on a retrospective basis for fiscal years, and interim periods within those years, beginning after December 15, 2011, which was the first quarter of 2012 for the Company. The adoption of this amendment resulted in a change to the Company’s current presentation of comprehensive income, but did not have any impact on the Company’s consolidated financial statements and related disclosures.

The FASB amended existing guidance by requiring that additional information be disclosed about items reclassified ("reclassification adjustments") out of accumulated other comprehensive income. The additional information includes separately stating the total change for each component of other comprehensive and separately disclosing both current-period other comprehensive income and reclassification adjustments. Entities are also required to present, either on the face of the income statement or in the notes to the financial statements, significant amounts reclassified out of accumulated other comprehensive income as separate line items of net income but only if the entire amount reclassified must be reclassified to net income in the same reporting period. For amounts that are not required to be reclassified in their entirety to net income, an entity must cross-reference to other disclosures that provide additional detail about those amounts. This accounting standard will be effective for interim and annual periods beginning after December 15, 2012. The Company does not believe the adoption of this update will have a material impact on its financial statements.