Some people record all their mileage on a calendar, planner, or business diary that they keep in their car. Be sure to jot down the date, the purpose of the trip, the starting and ending odometer readings, and the total number of miles driven. Another good source of documentation is a copy of the forms that you provide to your employer for expense reimbursement. Remember, you are entitled to deduct the difference between the IRS business mileage reimbursement rate (50.5 cents in 2008) and the mileage reimbursement rate provided by your employer.

Mileage expenses are also deductible for charitable, moving, or medical purposes. In 2008, the mileage rate for medical or moving purposes is 19 cents per mile driven. The mileage rate for service to a charitable organization is 14 cents per mile. As in the case of business mileage, written documentation should be kept of length and purpose of each trip.

We would like your feedback on this Personal Finance Frequently Asked Question.