That depends on whether you were reimbursed under an accountable plan or under a nonaccountable plan. Generally, an employer will have an accountable plan if it pays business expenses that would otherwise be deductible by the employee, requires the employee to substantiate the expense, and does not permit the employee to keep any reimbursements that exceed expenses. If the employer does not use an accountable plan, mileage reimbursement would be included in your wages on Form W-2. For more information on reimbursements and accountable plans, refer to Chapter 6 of Publication 463, Travel, Entertainment, Gift, and Car Expenses.

If your mileage reimbursement is included in box 1 on Form W-2, you need to enter that amount on the "wages, salaries, and tips" line of your tax return. If you itemize your deductions on Form 1040, Schedule A (PDF), Itemized Deductions, you may deduct the business transportation expense as an employee business expense, subject to the 2% limitation of adjusted gross income. You may usually deduct either your actual business automobile expenses or use the standard mileage rate. For more information on when you may use the standard mileage rate, refer to Chapter 4 of Publication 463, Travel, Entertainment, Gift, and Car Expenses.

References:

• Publication 463, Travel, Entertainment, Gift, and Car Expenses
• Publication 529, Miscellaneous Deductions
• Tax Topic 501, Should I itemize?
• Tax Topic 510, Business use of car
• Tax Topic 514, Employee business expenses

A Sole Proprietor's business use of a car or truck is claimed on line 10 of Form 1040, Schedule C (PDF), Schedule C, Profit or Loss from Business or, if eligible, line 2 of Form 1040, Schedule C-EZ (PDF), Net Profit from Business. You may use either the actual expense method in calculating your car or truck expense or, if eligible, the 2003 standard mileage rate of 36 cents per mile. Depreciation expense is already included in this standard mileage rate. Depreciation is only calculated as a separate expense when using the actual expense method. Deductible employee business use of a car or truck may be taken on Form 2106 (PDF), Employee Business Expenses , or if, eligible, line 1 of Form 2106-EZ (PDF), Unreimbursed Employee Business Expenses. The car and truck expenses are then taken with other employee business expenses on line 20, Form 1040, Schedule A&B (PDF) Itemized Deductions . For more information, refer to Publication 463, Travel, Entertainment, Gift, and Car Expenses , and Publication 535, Business Expenses .

References:

• Publication 535, Business Expenses
• Publication 463, Travel, Entertainment, Gift, and Car Expenses
• Form 1040, Schedule C (PDF), Profit or Loss from Business (Sole Proprietorship)
• Form 1040, Schedule C-EZ (PDF), Unreimbursed Employee Business Expenses.
• Form 2106 (PDF), Employee Business Expenses
• Form 2106EZ (PDF), Unreimbursed Employee Business Expenses