How to track business mileage for taxes (and keep an audit-ready log)
Business mileage is one of the most valuable deductions for anyone who drives for work — and one of the most commonly disallowed, because the records don't hold up. Here's what a defensible log actually needs.
What the IRS wants to see
For each business trip, a compliant log records: the date, the business purpose, the starting and ending point (or miles driven), and the business miles. You also need your total miles for the year and ideally your odometer reading at the start and end of the year. "Approximately 8,000 miles" written in December is exactly what gets thrown out.
Standard mileage vs actual expenses
You generally choose between the standard mileage rate (a set cents-per-mile that bundles gas, wear, insurance) and the actual expense method (your real vehicle costs × business-use percentage). Most sole operators take the standard rate because it needs only a mileage log, not a shoebox of receipts. Either way, the mileage log is the foundation — actual expenses still require business-use percentage, which comes from miles.
Track it as you go, not at tax time
The one rule that saves the deduction: log the trip when it happens. A contemporaneous record — entries made at or near the time of each trip — is what makes a log credible. Reconstructing a year from memory and calendar guesses is where deductions die.
The low-effort setup
A simple spreadsheet with date / purpose / from / to / miles works, and you can total it with SUMIFS by month or client. But a phone that captures trips automatically removes the discipline problem entirely — which is the point of Taxes Made Simple: audit-ready mileage logs plus receipt capture, so the record exists without you remembering to make it.
This is general information, not tax advice — confirm specifics for your situation with a tax professional.