I am assuming that you work as a rural mail carrier using your own vehicle.

If this is the case, you will need to deduct actual expenses if those expenses are less than any qualified reimbursement that you receive from the Postal Service. See the following from IRS Publication 463:

Rural mail carriers .   If you are a rural mail carrier, you may be able to treat the qualified reimbursement you received as your allowable expense. Because the qualified reimbursement is treated as paid under an accountable plan, your employer shouldn’t include the reimbursement in your income.

 If your vehicle expenses are more than the amount of your reimbursement, you can deduct the unreimbursed expenses as an itemized deduction on Schedule A (Form 1040). You must complete Form 2106 and attach it to your Form 1040, U.S. Individual Income Tax Return.

 A “qualified reimbursement” is the reimbursement you receive that meets both of the following conditions.

• It is given as an equipment maintenance allowance (EMA) to employees of the U.S. Postal Service.

• It is at the rate contained in the 1991 collective bargaining agreement. Any later agreement can’t increase the qualified reimbursement amount by more than the rate of inflation.

See your employer for information on your reimbursement.

If you are a rural mail carrier and received a qualified reimbursement, you can’t use the standard mileage rate.