Twelve weeks of records, five years of claiming. That is the trade the logbook method offers, and it is why the method is worth the effort even for people who find the twelve weeks tedious.
The five years are not unconditional, though, and the conditions are where the answers online diverge most sharply.
The five year rule
A logbook is generally valid for the income year in which it is kept and for the four following income years. Source: ATO, logbook method.
So a logbook kept during the 2026-27 income year can generally support claims for 2026-27, 2027-28, 2028-29, 2029-30 and 2030-31. Five income years in total, including the one it was kept in. Counting the logbook year as an extra year on top is the most common arithmetic mistake here.
You may also keep a new logbook earlier than that if you want to. A logbook that is still technically valid but is producing a percentage well below your current use is costing you money, and nothing stops you replacing it.
The condition attached to the five years
The percentage only carries forward while it still reflects how you use the car. The ATO’s test is that if your circumstances change and the logbook is no longer representative of your work-related use, you need to complete a new 12 week logbook.
That is the whole rule. There is no separate condition, no form to lodge, and no notification. It is a judgment you make about your own circumstances.
The ATO gives changing jobs and moving house as examples of circumstances that can make a logbook no longer representative. Both are obvious once stated and both are routinely missed, because neither feels like a tax event at the time.
Other changes with the same effect: moving from a field role to a desk role or the reverse, taking on or losing a territory, a change in the number of days you work from home, or picking up a second car for work.
The rule that does not exist
You will find sources stating that a logbook is invalidated if your business use changes by more than 10 percent.
There is no 10 percent rule in the individual income tax logbook requirements. That threshold comes from the fringe benefits tax operating cost method, which is a different regime with different tests, applied by employers to cars they provide. It has been repeated into the individual context often enough that it now reads as settled, and it is not.
This matters in both directions. Someone whose use shifted by 12 percent may conclude a perfectly valid logbook is void and stop claiming. Someone whose use shifted by 8 percent may conclude they are safe when the logbook is no longer representative at all.
The actual test has no number in it: is the logbook still broadly representative of your work use? That is a judgment about your circumstances, not a calculation. If your work pattern has genuinely changed, keep a new logbook. If it has not, the old one stands.
What you still have to do in the four later years
The logbook itself is not the only record. In each income year you use the method, you also need:
- odometer readings for the start and end of the period you held the car in that year
- the work-related kilometres you travelled
- your business-use percentage
This is the obligation people miss, because the logbook period is over and it feels finished. It is not. Miss the annual odometer readings and you have a valid logbook supporting a year you cannot substantiate. Details in what odometer readings you need.
Changing cars
If you replace the car, the old logbook belongs to the old car. A new car has its own odometer chain and its own record, and it is also a change in your circumstances.
If you run more than one car for work, each needs its own logbook, and where logbooks are kept for two or more cars they must cover the same period. Adding a second work car is therefore not a small administrative change: it is a trigger for a fresh twelve weeks across the vehicles.
Keeping the record after the five years
Validity and retention are different clocks, and conflating them is the other common error on this topic. A logbook you last relied on in 2030-31 has to be kept well past 2030-31. See how long to keep your logbook and receipts.
In practice
Set a reminder for the fifth year. A logbook quietly expiring is not something anyone tells you about, and the first year you notice is usually the year you are trying to lodge.
Between now and then, the question to revisit each year is short: has anything changed about my work, my home, or my cars that would make these twelve weeks a poor description of the year I just had? If yes, twelve more weeks. If no, carry on.