ATO Logbook Method: 12-Week Guide
The logbook method is the alternative to cents-per-km for drivers who exceed the 5,000 km cap or have high actual vehicle costs. It requires a 12-week representative logbook plus documentation of all vehicle expenses for the year.
The 12-week logbook
You must keep a logbook for at least 12 consecutive weeks that represents your typical business driving. The 12 weeks do not have to be at the start of the financial year - they need to be representative.
For each trip during those 12 weeks: date, destination, purpose, and odometer reading at start and end. Total kilometres for the period (business and personal) and start-of-period and end-of-period odometer readings.
Calculating business-use percentage
From the 12-week logbook, calculate: business kilometres ÷ total kilometres for the period × 100 = business-use percentage. That percentage is then applied to all of your vehicle expenses for the full financial year.
Example: 12-week period shows 4,800 business km out of 6,000 total km. Business-use percentage is 80 percent. If your full-year vehicle expenses (fuel, insurance, registration, depreciation, maintenance) total $14,000, your deduction is $14,000 × 80% = $11,200.
Logbook validity
A logbook is valid for five financial years from the year it was completed, provided your driving pattern has not materially changed. If you change jobs, move to a different city, or significantly alter your driving routine, you need a new 12-week logbook.
If circumstances are stable, the 12 weeks of work in year one carry the deduction methodology for years two through five.
What expenses qualify
Fuel and oil. Insurance. Registration. Maintenance and repairs. Depreciation (calculated using ATO depreciation rules, typically diminishing-value method on the cost base). Loan interest if the vehicle was financed (the business-use portion). Lease payments (the business-use portion) if the vehicle was leased instead of owned.
FAQ
Can I switch from cents-per-km to logbook mid-year?
You choose your method when you lodge your tax return, not at the start of the year. So you can decide in retrospect which method produces the larger deduction for the year just ended, provided you have the records to support each method.
What if I forget to start the logbook in the right window?
Start one immediately. As long as the 12-week period is representative of your typical driving, the ATO will accept it. The risk is if you start it during an atypical period (heavy holiday driving, illness affecting normal driving) - that would skew the business-use percentage.
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