Haven't Started a Logbook This Financial Year? September Is the Month to Do It
We're two months into the 2026–27 financial year. If you drive your own car for work and you're planning to claim more than the cents-per-kilometre method allows, there is one thing you need to have done by 30 June next year: kept a logbook for 12 continuous weeks. September is close to the ideal time to start it, and here's why.
The 12 weeks have to be representative
The ATO's rule is that a first-year logbook must cover at least 12 continuous weeks, and that period needs to reflect your travel across the whole year. That's the catch with leaving it late. Start in early December and your logbook straddles the Christmas shutdown, January holidays and a stretch where most people drive less for work and more for pleasure. Start in April and you're racing the 30 June deadline. Start this week and you finish in late November, with a clean run of ordinary working weeks behind you.
Why bother with a logbook at all?
Because the cents-per-kilometre method has a ceiling. For 2026–27 the rate is 91 cents per kilometre, capped at 5,000 business kilometres per car, which puts the maximum claim at $4,550. If you drive more than 5,000 work kilometres, or your car costs more to run than 91 cents a kilometre covers, the logbook method is the only way to claim your actual business share of fuel, servicing, insurance, registration, interest and depreciation. For a tradie or sales rep doing 15,000 business kilometres a year in a $50,000 ute, the difference is routinely thousands of dollars.
What the logbook actually has to record
The ATO is specific. For the logbook period as a whole: the start and end dates, the odometer reading at each end, the total kilometres travelled, and your resulting business-use percentage. For every journey: the date, the reason for the trip (or that it was private), the odometer at the start and finish, and the kilometres. You also need the car's make, model, engine capacity and registration number. Back-to-back work trips on the same day can be recorded as one journey. Miss the odometer readings and the whole thing is unsupported; that is the single most common reason a logbook fails at audit.
It's valid for five years
This is the part people underrate. Do the 12 weeks once and the business-use percentage it produces can be applied to your car expenses for that year and the next four, provided your circumstances stay broadly the same. Change jobs, move house, or shift from site work to a desk and the percentage stops being representative and you need a fresh logbook. Otherwise, one focused quarter buys you five years of claims.
The part that quietly voids old logbooks
Even with a valid five-year logbook, the ATO still requires the odometer reading at the start and end of every income year the logbook is used for. A perfectly good logbook from 2024 is useless for your 2026–27 return if nobody wrote down the odometer on 1 July 2026 and 30 June 2027. If you've got an existing logbook and skipped this, take a photo of the dash today and note the date; a reading in early September is far better evidence than none.
Started using the car for work recently?
If you began driving for work less than 12 weeks before 30 June, the ATO lets you run the logbook into the following income year so it still reaches 12 continuous weeks. The same logic applies now: anyone who picked up a new role in July or August has no reason to wait.
Two cars, one period
If you want the logbook method for more than one vehicle, each car's logbook must cover the same 12 weeks, and that period has to be representative of the business use of all of them. Pick one window and run every car through it.
Paper still works, but it rarely survives
The ATO accepts a pre-printed logbook from the newsagent or any electronic equivalent. The practical problem with paper is the 5.45pm trip home when nobody writes anything down, and the odometer reading that gets rounded from memory a week later. An app like Odomly records each trip's start and end odometer automatically, tags it business or private, and stamps the 1 July and 30 June readings so the five-year validity isn't lost to a forgotten photo. Whatever you use, the rules are the same. What changes is whether the record exists when the ATO asks for it.
The short version
Open a logbook this week, keep it for 12 continuous weeks through to late November, record every trip with odometer readings, and photograph the odometer on 1 July and 30 June each year for as long as you rely on it. Do that once and your 2026–27 return, and the four after it, are covered.
This article is general information, not tax advice. Rates and rules are current as at September 2026 — check ato.gov.au or speak to a registered tax agent about your own situation.