The car logbook 12-week rule, explained

Last reviewed 29 October 2026 · Sources linked below · Written by Jay at Andwat Co, an Australian boilermaker/fabricator (Cert III Engineering, 12+ years in the trade). About

What a valid ATO car logbook must record, how the 12 continuous weeks work, how long a logbook lasts, and how to turn it into a business-use percentage.

Sole traders and some partnerships can claim car expenses using either the cents per kilometre method or the logbook method. The logbook method lets you claim the business share of your actual car costs, such as fuel, rego, insurance, servicing, tyres and depreciation. To use it you need a valid logbook.

The 12-week rule

• In the first year you use the logbook method, keep a logbook for at least 12 continuous weeks.
• Those 12 weeks must be representative of your normal travel for the year. Don't pick your busiest run of site visits.
• If you started using the car for business less than 12 weeks before 30 June, you can keep going into the next year until you have 12 continuous weeks.
• A logbook is valid for five years. Start a new one if your work changes and the old one no longer reflects how you use the car.
• If you use the logbook method for two or more cars, the logbooks must cover the same period.

What the logbook must record

For the logbook period:

• the start and end dates of the logbook period
• the odometer readings at the start and end of the period
• the total kilometres travelled in the period
• your business-use percentage for the period
• the car's make, model, engine capacity and registration number
• the odometer readings at the start and end of each later income year that you rely on the logbook for.

For each journey:

• the reason for the trip (the business reason, or that it was private)
• the start and end date
• the odometer readings at the start and end
• the kilometres travelled.

The ATO allows two or more journeys in a row on the same day to be recorded as one journey. You can keep the logbook on paper or electronically, for example with myDeductions in the ATO app.

Turning it into a claim

Business-use % = business km ÷ total km × 100. Then multiply your total car expenses for the year by that percentage.

Records to keep as well

• Receipts for fuel and oil, or odometer-based estimates of them, plus receipts for other car costs.
• Evidence of all your other car expenses.
• If you rely on a logbook from an earlier year, keep that logbook and keep recording your odometer readings each year.

Sources

• ATO – Logbook method (sole traders and partnerships)
• ATO – Logbook method (individuals)
• ATO – Motor vehicle expense calculation methods

Related guides

• Simpler BAS: what goes in G1, 1A and 1B
• How to quote a job with GST (Australia)

General information only, summarised from the official sources above as at the review date. It isn't legal, tax, WHS or engineering advice. Rules change and your situation may differ, so check the source or ask a professional.