IRS Mileage Log Requirements: What You Need to Track in 2026

Of all the paperwork involved in claiming a mileage deduction or receiving a tax-free reimbursement, the mileage log is the most important document you'll produce. Get it wrong — or skip it — and you risk losing your deduction entirely if audited.

The good news: the IRS requirements are actually quite straightforward. Here's exactly what you need.

What the IRS Requires in a Mileage Log

Under IRS Publication 463, a valid mileage record must contain the following information for each business trip:

The IRS also expects you to have a record of your total annual vehicle miles — usually captured by noting your odometer reading on January 1 and December 31 of each year. This establishes the business-use percentage of your vehicle.

What Does "Contemporaneous" Actually Mean?

The IRS requires records to be "recorded at or near the time of the expense." This doesn't mean you have to pull over and write in a paper journal while still in the parking lot — but it does mean:

• Recording trips daily or within a day or two is fine
• Logging a week's worth of trips on Sunday evening from memory is generally acceptable with supporting evidence (calendar entries, emails, GPS data)
• Reconstructing 12 months of trips from memory in April when you file is not contemporaneous and will not survive an audit

Acceptable Formats for a Mileage Log

The IRS does not require a specific form or format. All of the following are acceptable:

• Paper journal or notebook: Old-fashioned but perfectly valid
• Spreadsheet (Google Sheets or Excel): Popular because it's easy to total miles and calculate reimbursement
• Mileage tracking app: MileIQ, Everlance, Stride, TripLog — GPS-based apps create automatic logs with timestamps and route maps, which is excellent audit documentation
• Printed mileage log: Like the one generated by our free mileage log tool
• Calendar-based records: If your calendar entries show client names, locations, and dates that align with your mileage claims, this can supplement other records

What Happens if You Don't Have a Mileage Log?

If you're audited and can't produce a contemporaneous log, the IRS can disallow your entire mileage deduction — even if you genuinely drove those miles for business. The burden of proof is on you, not the IRS.

In some cases, the IRS may allow a reconstructed log based on other evidence (appointment calendars, client emails, GPS data, credit card records from business locations), but this is not guaranteed and requires more work than simply keeping the log in the first place.

How Long to Keep Mileage Records

As a practical matter, keeping vehicle records for 4 years after filing covers the standard 3-year statute of limitations with a buffer. Store digital backups — cloud storage or email to yourself — so records aren't lost if your phone breaks or computer crashes.

Special Rules for Mixed Business/Personal Use

If you use the same vehicle for both business and personal trips (which most people do), you need to track both. Your total annual miles establishes the denominator; your business miles are the numerator. The resulting percentage applies if you're using the actual expense method. For the standard mileage rate, you simply multiply business miles × $0.70 and the personal miles are irrelevant for the deduction calculation.