What an IRS mileage log needs
If you deduct business miles, the IRS expects a record you made as you went, not a number you reconstruct at tax time. Here is what that record should contain, the mistakes that weaken it, and how an automatic log helps.
What a mileage log should contain
IRS Publication 463 (Travel, Gift, and Car Expenses), in its recordkeeping chapter, describes the information that supports car expenses. For each business trip, record:
| Field | What to write |
|---|---|
| Date | The day you drove. |
| Destination | Where you went: a business name, a client site, or an address or city. |
| Business purpose | Why you went. Specific beats vague: "Quarterly review with a client" rather than "meeting". |
| Miles | The miles driven for that business use. |
Pub 463 also asks you to be able to show your total miles for the year on that vehicle, so the business share can be seen against all driving, and it discusses how the figures are used for the standard mileage rate and for actual expenses. Read the current edition for the exact wording.
Keep it as you go
The IRS puts more weight on a record made at or near the time of the trip than on a summary prepared much later. A paper log, a diary, a spreadsheet or an app can all work, as long as the entries are accurate and kept regularly. The point is that the record is credible if someone checks it.
Common mistakes
- Counting commute miles. Driving between home and a regular workplace is generally commuting, which is not deductible business mileage. Trips between work locations, or to a client from your workplace, are a different matter. Ask your tax professional how your situation is treated.
- Leaving out the purpose. A date and a mileage total with no reason for the trip is the weakest kind of entry.
- Vague purposes. "Business", "meeting" and "errands" do not tell a reviewer much.
- Reconstructing the log later. Filling in a year of trips from memory or a calendar tends to produce round numbers and gaps.
- Mixing business and personal stops. If a trip includes a personal stop, the log should make clear which miles were business.
- No total-mileage figure. Business miles are easier to defend when the vehicle's total miles for the year are on record.
How SimpliExpense helps
- It records drives as they happen. Drives are detected in the background using motion and location, so entries exist at the time of the trip.
- A business purpose is required. A business item cannot enter a report without one.
- Commutes stay personal. A home-to-office commute rule marks those drives Personal, and work-hours and local-errand rules sort other drives.
- Reviewers can check the trips. Report PDFs can link each From and To to Google Maps and the miles to the route. Toggle this in Settings.
- Reports flag anything unusual. Every date shows its weekday, and items on weekends, US federal holidays, or outside your work hours get a flag.
- Split trips are marked. A gas or coffee stop splits a trip; the next leg is labeled as a continuation and reports mark it.
- Submitted records lock. Once a report is submitted, its drives, expenses and the report itself can no longer change.
Routes and coordinates stay on your device. The report contains the fields the IRS expects, but you remain responsible for the accuracy of your entries.
SimpliExpense provides record-keeping tools. This page is general information, not tax, legal, or accounting advice. Confirm how the rules apply to you with a tax professional.
IRS sources
- IRS Publication 463, Travel, Gift, and Car Expenses
- IRS: Standard mileage rates. See also our page on the 2026 IRS mileage rates.