IRS Mileage Log Requirements and Audit Tips
What the IRS expects in a mileage log, how to keep compliant records, and practical tips to avoid audit issues.
Tripbook teamUpdated · 3 min read All guides
If you deduct business mileage or request reimbursement, the IRS expects clear, contemporaneous records. A solid mileage log protects deductions, makes reimbursements non‑taxable, and reduces audit risk.
This guide summarizes what the IRS expects and how to keep records that stand up to scrutiny.
What the IRS requires in a mileage log
The IRS requires adequate records that show the amount, time, place, and business purpose of each trip. These records should be made at or near the time of the expense and kept in a consistent log (paper, spreadsheet, or app).
At a minimum, record:
- Date of the trip
- Start and end location
- Odometer readings (or total miles)
- Business purpose of the trip
- Whether the trip was business or personal
An annotated mileage log
This is what a complete week looks like for a self-employed consultant with one car. Each column answers one of the IRS’s four questions: amount, time, place and business purpose.
| Date | From → To | Business purpose | Odometer start | Odometer end | Miles | Type |
|---|---|---|---|---|---|---|
| Jul 6, 2026 | Home office → Baker & Co, Round Rock | Quarterly review with Jane Baker | 41,210 | 41,232 | 22 | Business |
| Jul 6, 2026 | Baker & Co → Home office | Return | 41,232 | 41,254 | 22 | Business |
| Jul 8, 2026 | Home office → Supplier, San Marcos | Collect sample stock | 41,254 | 41,285 | 31 | Business |
| Jul 8, 2026 | Supplier → Grocery store, Kyle | Personal errand | 41,285 | 41,297 | 12 | Personal |
| Jul 10, 2026 | Home office → Bank, Austin | Deposit client checks | 41,297 | 41,305 | 8 | Business |
What makes it hold up:
- Purpose names the business reason, not just “meeting”. A client name or job number lets someone check it against an invoice.
- Personal trips are logged too. A log with no personal miles for a car you use daily looks rebuilt.
- Odometer readings chain. Each trip starts where the last one ended, so gaps stand out.
- The trips from home count as business here because the home office is the consultant’s principal place of business. Without it, the first and last trips of the day would be commuting.
The free IRS mileage log template has these columns and calculates the totals.
More than one vehicle
Keep a separate log per vehicle, and record each vehicle’s odometer on January 1 and December 31. If you use the standard mileage rate, you choose it per vehicle in the first year that vehicle is used for business. Switching trips between cars in one log makes the odometer chain impossible to check.
How long to keep the log
Keep your mileage log and supporting records for as long as the IRS can examine the return: generally three years from the date you filed. If you use actual expenses and depreciate the vehicle, keep the records for as long as you own it plus that period, because depreciation carries forward.
Keep your log up to date
The IRS trusts logs made at the time of the trip. A mileage log you update regularly (daily or weekly) is much stronger than a log rebuilt months later from memory.
Receipts and supporting documents
Mileage logs are the core record, but you should also keep supporting evidence such as calendars, client emails, invoices, or job tickets that show the business purpose and timing of trips. The IRS allows reasonable methods of substantiation, but your records must be specific and consistent.
Common audit issues (and how to avoid them)
- Commuting counted as business mileage: Regular travel between home and your main workplace is commuting, not deductible business mileage.
- Missing purpose: Logs that list only miles without a business reason can be disallowed.
- Inconsistent totals: Large differences between logs, calendar entries, and reported mileage raise questions.
- Reconstructed logs: Backfilled logs are less credible than contemporaneous records. If you need to rebuild a past log, see our guide on what to do if you forgot to track mileage.
Practical tips to stay compliant
- Log trips the same day you drive
- Note the business purpose in plain language
- Keep a simple backup trail (calendar, emails, invoices)
- Separate commuting from business miles
- Store your log for at least the tax recordkeeping period
If you want to see how mileage reimbursement is calculated or which rate to use, read our IRS Mileage Reimbursement Guide and Mileage Tracking Guide. For a deeper look at what happens when the IRS questions your mileage records, see our IRS mileage audit defense guide.