For 2025 the IRS optional business rate is 70 cents per mile. That figure is meant to cover depreciation, maintenance, insurance and fuel. Charitable, medical and moving rates are lower and are a different deduction.
A contemporaneous record — date, destination, business purpose, miles — is what survives an exam. Reconstructing a year from calendar invites is how deductions get reduced.
Actual expenses
You may use actual expenses instead, but switching methods after the first year you own the car is restricted. Ask a tax professional before you change. Estimate the standard-rate figure with the IRS mileage calculator and keep the trips in CarDiary.
Commuting
Home to a regular workplace is not business mileage. A trip from the office to a client site usually is.
