The IRS does not just take your word for how many miles you drove. If you claim the mileage deduction, you need a log that backs it up — and if it is missing key details, the IRS can reject the entire deduction during an audit. The good news: the rules are simple once you know them. Here is exactly what your mileage records must include in 2026, straight from IRS Publication 463, plus the mistakes that get deductions thrown out.

The 5 things every mileage log must record

For each business trip, the IRS expects your log to show:

1. The date of the trip.
2. The miles driven for that trip (your business mileage).
3. The destination (where you drove).
4. The business purpose (why the trip was for work).
5. Your total annual mileage — the odometer readings that let you separate business miles from personal miles over the year.

Miss any one of these on a regular basis and your log stops being “adequate” in the eyes of the IRS. All five are worth getting right, because the deduction can be large: at the 2026 IRS standard mileage rate, every 1,000 business miles is a meaningful write-off.

Records must be “contemporaneous”

This is the rule people miss. The IRS wants a log kept at or near the time of each trip — not one you reconstruct from memory in April. A record made the day of (or the same week as) the drive is far stronger than a spreadsheet you fill in a year later. This single word, contemporaneous, is why automatic tracking apps are so useful: they timestamp every drive as it happens, so your log is always current.

What a compliant log entry looks like

Date	Destination	Purpose	Miles
03/14/2026	Client office, downtown	Client meeting	18.4
03/15/2026	Supply warehouse	Pick up inventory	7.2

Plus your odometer at the start and end of the year so you can show total miles and the business share.

Common mistakes that get deductions rejected

• No business purpose — “drove 20 miles” is not enough; the IRS wants to know why.
• Round numbers everywhere — a log that is all “10, 20, 30” looks estimated, not measured.
• Reconstructed after the fact — a log built from memory at tax time is the weakest kind.
• Mixing personal and business — only business miles are deductible; you must be able to separate them.
• No odometer / total miles — without your yearly total, the IRS cannot verify the business percentage.

Paper log vs app: both are allowed

The IRS accepts a paper logbook, a spreadsheet, or a mileage-tracking app — what matters is that the record is accurate and contemporaneous. A paper log works if you are disciplined about filling it in every trip. Most people are not, which is where an app helps: it records each drive automatically with the date, distance, and route, so all you add is the purpose. If you want to start on paper, grab our free IRS-compliant mileage log template. When you are ready to automate it, see the best mileage tracker apps for 2026.

How to keep a compliant log with less effort

The whole point of the rules is provability. An automatic tracker gives you that with almost no work: it logs the date, miles, and destination for every drive, you tap a purpose, and at tax time you export an IRS-ready report. For a step-by-step on pulling that report, see how to export a mileage report for taxes, or the bigger-picture guide on how to track mileage for taxes in 2026.

Which miles actually count as business miles?

Only business miles are deductible, and the definition trips people up. Driving from your home to your regular workplace is commuting, and commuting is not deductible. But driving from your office to a client, between job sites, to the bank for the business, or to pick up supplies — those are business miles. If you work from a home office that is your principal place of business, trips from there to work locations can count too. When in doubt, write down the purpose; it forces you to decide honestly whether a trip was really for work.

Your records depend on which deduction method you use

There are two ways to deduct car costs, and they need slightly different records:

• Standard mileage method — you multiply business miles by the IRS rate. This needs a solid mileage log (the five fields above). It is simpler and what most drivers use.
• Actual expense method — you deduct the business share of real costs (gas, insurance, repairs, depreciation). This still needs your mileage log to prove the business-use percentage, plus receipts for every expense.

Either way, the mileage log is the foundation. Without it, you cannot support either method. For a full walkthrough, see our guide on how to track mileage for taxes in 2026.

Digital log best practices

• Log every trip the day it happens — keeps your record contemporaneous.
• Add the purpose while it is fresh — a one-line reason is all you need.
• Back up your data — export a copy so a lost phone never means a lost deduction.
• Reconcile with your odometer at the start and end of the year.

Want to estimate your deduction first? Try our mileage deduction calculator.

Frequently asked questions

What information does the IRS require in a mileage log?

For each business trip: the date, the miles driven, the destination, and the business purpose — plus your total annual mileage (odometer readings) so business and personal miles can be separated. This follows IRS Publication 463.

Does the IRS require a contemporaneous mileage log?

Yes. The IRS wants records kept at or near the time of each trip. A log reconstructed from memory at tax time is much weaker and more likely to be challenged in an audit.

Is a mileage tracking app IRS-compliant?

Yes, if it records the required details (date, miles, destination, purpose) and you keep it current. Apps are often stronger than paper logs because they timestamp every drive automatically.

Can the IRS reject my whole mileage deduction?

Yes. If your log is missing required details or looks estimated rather than contemporaneous, the IRS can disallow the deduction. Complete, timely records are your protection.

Do I need odometer readings?

You need enough to establish your total annual mileage and business percentage — typically odometer readings at the start and end of the year, plus per-trip business miles.

How long should I keep my mileage records?

Keep mileage logs for at least three years from the date you file the return, since that is the general IRS audit window.

Skip the paperwork — Mileafy logs every trip automatically with the date, distance, and destination the IRS wants.