IRS Mileage Log Requirements

IRS Mileage Log Requirements
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If you use your own vehicle to travel for business or medical purposes, you may qualify to deduct a portion of your expenses from your taxable income. However, the Internal Revenue Service does not allow taxpayers to deduct expenses they have estimated. For this reason, you must keep an accurate and detailed log of your medical and business mileage throughout the year.

Purpose of Mileage Log

To claim a deduction for transportation expenses related to business or medical care, you must be able to provide the IRS with the exact number of miles you traveled during the year. The list must also be itemized based on the reason for each time you traveled. In the event of an audit, the IRS will request a copy of your mileage log to verify each of your deductions. If you cannot supply this information, the IRS may require you to submit an amended tax return.

Appropriate Documentation

The IRS requires taxpayers taking deductions for transportation expenses to record the mileage they travel during the year using trip sheets, statements of expense, logs, diaries, account books or similar records. Your mileage log should be professional in appearance and easy to understand -- incomplete or unprofessional mileage records can lead to problems in the event of an audit.

Recording Mileage

It's important to keep complete and accurate records of your mileage.
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Your mileage log should include the exact mileage you traveled during each qualifying trip you made, as well as the total number of miles you traveled during the year. The log should also include the date you made each trip and the name of the destination to which you were traveling. Finally, the log should contain the purpose of the trip with an explanation of how it relates to your business.

Claiming a Deduction

When you claim your deductions for medical and business transportation expenses, you can calculate each deduction using either the standard mileage rate or the amount of each qualifying transportation expense. Using the standard mileage rate, you will deduct a flat amount of money for each qualifying mile you traveled. Using the amount of your individual expenses, you will deduct the percentage of each qualifying expense that related to qualifying miles. For example, if 40 percent of your total mileage qualified as business mileage, you can deduct 40 percent of each qualifying expense. Regardless of the method you choose, you must use information from your mileage log to complete the calculation.


Because qualifying expenses and standard mileage rates differ, taxpayers should keep separate mileage logs for business and medical travel. For example, insurance is a qualifying expense for business travel, but it is not a qualifying expense for medical travel. Taxpayers must also calculate business and medical deductions separately.