Logbook Method
Quick definition
Keeping a 12-week sample log to establish business-use percentage. Used by CRA in Canada and ATO in Australia.
The logbook method is the international (non-US) approach to verifying business-use percentage. It requires keeping a representative sample log of trips for a defined period (typically 12 weeks), then applying that percentage to total annual miles.
How it works
You log every trip. Business and personal. For 12 consecutive weeks. The resulting business-use percentage is then applied to your total annual mileage and vehicle costs. The 12-week sample is valid for up to five years if your driving pattern stays consistent.
Where it applies
The Canadian CRA and Australian ATO both use a logbook method. See the ATO logbook guide. CRA logbook rules are described here. The IRS does not require a 12-week sample; US drivers maintain a year-round log.
Why it differs from US practice
US drivers get to use the simpler standard mileage rate, which does not require a business-use percentage at all (just the per-business-mile count). International drivers do not have that simplification, so a sample-based logbook is the practical workaround.
Related terms
Business-Use Percentage
Business miles divided by total miles. Used to scale the actual-expenses deduction.
Contemporaneous Log
A mileage log created at or near the time of the trip. What the IRS expects to see in an audit.
Cents per Kilometre
Australia's simplest mileage deduction method. A flat per-km rate up to 5,000 km per year.
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