Short answer
In an audit, car expenses must be backed by adequate records or sufficient corroborating evidence (section 274(d)): for each business trip, the date, the destination, the business purpose and the miles, plus your total miles for the year. If you have no log, rebuild one only from records made at the time, such as location history, say how it was built, and get a tax professional involved.
What does the IRS ask for in a mileage audit?
Usually a written request for documents: your mileage log for the year under review, and sometimes the evidence behind it. Vehicle expenses fall under the strict substantiation rules, so the examiner looks for:
- The date, destination and business purpose of each business trip.
- The miles of each trip, and the total miles driven in the year.
- Records made at or near the time of the trips, or other evidence that corroborates them.
Can you rebuild a log after receiving the audit letter?
You can rebuild it, as long as everything in it comes from records made at the time and you say it was rebuilt. A log written from memory after the letter arrived carries little weight. The method is in our guide to reconstruct a mileage log.
What should you hand the examiner?
| Document | Why |
|---|---|
| The mileage log, every trip of the year | Business, commuting and personal miles that add up |
| A short statement of how it was built | Shows the trips come from data recorded at the time |
| The source export (Timeline file) | Lets the dates and distances be checked |
| Odometer readings for the year | Confirms the total miles |
| Invoices or calendar entries for the business trips | Corroborates the purposes |
The Google Maps Timeline mileage log prints the method statement on the log itself, with odometer readings and parking and tolls. When the audit covers several years, the all-years pack unlocks every year in your file for $79.
What should you avoid?
- Adding trips that no record shows, or rounding distances up.
- Presenting a rebuilt log as one kept day by day.
- Answering alone when the amounts are large: an enrolled agent or CPA can represent you.
Common questions
The IRS asked for my mileage log and I never kept one. What now?
Do not invent one. Gather records made at the time (location history, calendar, invoices, odometer readings), rebuild the log from them, say plainly that it was reconstructed and how, and talk to a tax professional before you answer.
Can the IRS estimate my mileage if my records are incomplete?
For car expenses, generally not. Section 274(d) requires adequate records or sufficient evidence corroborating your own statement; the courts' usual allowance for reasonable estimates does not apply to these expenses.
Is a log built from Google Maps Timeline guaranteed to be accepted?
No tool can guarantee that. What it gives you is a record whose dates, places and distances were captured by your phone at the time, which is the kind of evidence the rules call for. The examiner decides.