Contemporaneous Log
Quick definition
A mileage log created at or near the time of the trip. What the IRS expects to see in an audit.
"Contemporaneous" means created at or near the time of the trip. The IRS uses this word to describe mileage logs that hold up under audit. Reconstructed logs (built in March from memory) generally do not.
Why it matters
The Tax Court has ruled against drivers in dozens of cases where the only mileage record was a year-end reconstruction, even when the underlying business activity was real. A contemporaneous log is the difference between a deduction the IRS questions and one they accept. See full log requirements.
What counts as contemporaneous
- A note logged the day of the trip: definitely contemporaneous.
- A note logged within a week of the trip: generally accepted as contemporaneous.
- A spreadsheet built in March from memory and old calendar entries: NOT contemporaneous.
- An auto-tracking app that timestamps trips at the moment of the drive: contemporaneous by construction.
Why apps win
A purpose-built mileage app records each trip the second it happens. There is no question of contemporaneousness. Paper logs and spreadsheets require discipline; the trip has to be entered before memory fades.
Related terms
Business Purpose
The IRS-required reason for a drive. Without a business purpose, the mile is personal.
Logbook Method
Keeping a 12-week sample log to establish business-use percentage. Used by CRA in Canada and ATO in Australia.
IRS Audit
A review of a tax return. Mileage deductions are one of the most-questioned line items.
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