What does the CRA require me to keep in a mileage log?
The CRA expects a mileage log that is detailed enough to verify business use of your vehicle. For each business trip, the log should record the date, the starting point and destination, the business purpose of the trip, and the number of kilometres driven. You should also note the odometer reading at the beginning and end of each year to establish total kilometres.
The log must be contemporaneous — kept as trips happen — rather than reconstructed from memory at tax time. Reconstructed logs are given little weight by the CRA and tax courts if a deduction is challenged. Digital apps that track GPS-based mileage can serve as logbooks provided they capture the required information.
Some taxpayers use a "simplified logbook" method: you maintain a full logbook for a base year, and in subsequent years you keep a three-month representative logbook to verify that your business-use percentage has not changed significantly. If your usage varies year to year, a full annual log is safer. Without a defensible log, the CRA can deny the vehicle deduction or assess it at a much lower percentage than claimed.
Key takeaways
- Each entry must include date, destination, business purpose, and kilometres driven.
- Year-start and year-end odometer readings establish your total kilometres.
- The log must be contemporaneous — recorded at the time, not reconstructed later.
- A simplified three-month logbook can be used in subsequent years if usage patterns are consistent.