Records
Standard mileage deduction
A per-mile rate that stands in for the actual cost of operating a vehicle for business.
You may deduct either actual vehicle costs or a standard rate per business mile. The standard rate absorbs fuel, maintenance, insurance and depreciation, so you cannot claim those separately on top of it.
The rate is set annually. Commuting between home and a regular workplace is never deductible; travel between work locations generally is.
Substantiation is per trip, not per year: date, miles, destination and business purpose. Publication 463 is explicit that a reconstructed annual total is not a record.
In Contha
Contha holds a log per trip and keeps undefended miles out of the deduction rather than quietly counting them, and prices the gap so you can see what the missing detail is worth.