Made a Mistake on Your Tax Return? How to Fix It Without the Stress
Forgot some interest or a deduction on your 2025-26 return? You can amend it online through myGov. Here's how, how long you've got, and what it costs.
Millions of Australians lodged their 2025-26 tax return in July or August. A good chunk of them are now discovering something they missed: a bank interest statement that turned up late, a union fee they forgot about, a donation receipt at the bottom of a drawer.
If that's you, relax. Fixing a lodged return is routine, it's usually done online in a few minutes, and the Australian Taxation Office (ATO) treats people who correct their own mistakes far better than people it has to chase. Here's how it works in plain English.
What amending actually means
Amending is simply asking the ATO to change the return you already lodged. You don't start again from scratch and you don't lodge a fresh return. You change only the numbers that were wrong, and the ATO reworks your tax and sends you an amended notice of assessment (the official letter showing how much tax you owe or get back).
It works in both directions. You can amend to add income you left out, which usually means paying a bit more, or to add a deduction or offset you missed, which usually means getting a bit more back.
The trap: don't lodge a second return
The most common mistake is lodging a whole new return to fix the first one. Don't. A second lodgment for the same year creates a mess that takes longer to untangle. Use the amend option instead, and wait until your original return has been processed and your notice of assessment has arrived before you do.
How long you've got
Most individuals have two years to amend. The clock starts the day after your notice of assessment is sent to you, not the day you lodged, and not 30 June.
So if your 2025-26 notice of assessment landed in your myGov inbox on 5 August 2026, your two-year window starts on 6 August 2026 and runs until early August 2028. The same rule applies to older years, so if your 2024-25 assessment issued within the last two years, you can still fix that one too.
Some people with more complex affairs get longer, and the ATO can go back further in cases of fraud or evasion. But for a typical wage earner, two years is the number to remember. Miss it and you generally lose the chance to claim a forgotten deduction.
How to do it online
It doesn't matter whether you lodged yourself or through someone else. If you have a myGov account linked to the ATO, you can request an amendment online:
- Sign in to myGov and open ATO online services.
- Go to your income tax lodgments and select Amend next to the income year you want to fix.
- Change the amounts that were wrong, or add the income, deduction or offset you missed.
- Check the new estimate at the end, then submit.
The ATO says an online amendment takes about 20 days to process. If you can't do it online, you can post the paper form, Request for amendment of income tax return for individuals, but that can take up to 50 business days.
If a registered tax agent lodged your return, the simplest route is to ask them to lodge the amendment for you. They can do it through their own systems, and their fee for doing it is generally deductible next year.
Worked example: Priya's forgotten interest and union fees
Priya earns an $80,000 salary. She lodged her 2025-26 return on 20 July 2026, before all her pre-fill data had arrived. In September she realises two things were missing.
First, $600 of interest from a savings account. At her income she sits in the 30% tax bracket for 2025-26, plus the 2% Medicare levy. So that $600 adds $180 of income tax and $12 of Medicare levy: $192 more to pay.
Second, $400 of union fees she's entitled to claim. A deduction reduces taxable income at the same combined rate, so it saves her $120 of income tax and $8 of Medicare levy: $128 back.
She fixes both in a single amendment. Her taxable income goes from $80,000 to $80,200, and the net result is $64 more tax (32% of the extra $200). One amendment, both errors fixed, and a much smaller number than she feared.
If she'd left the interest out, the ATO's data-matching would very likely have picked it up anyway, since banks report interest directly to the ATO. But she'd probably have missed out on the $128 union fee deduction entirely, because nobody reports those to the ATO for you.
Fixing it yourself is treated better
If your amendment increases the tax you owe, the ATO treats it as a voluntary disclosure. Owning up before the ATO finds an error generally means lower penalties, or none, compared with being caught by data-matching. Honest mistakes corrected promptly are exactly what the system expects.
Will you pay interest?
If your amendment means you owe more, the ATO can apply a shortfall interest charge. It covers the period between when your original tax was due and when the amended assessment issues. It's set 4 percentage points lower than the general interest charge the ATO applies to overdue debts, and on a small correction made within weeks it's usually a few dollars.
The longer you leave a known error, the more that charge builds up. So once you spot a problem, fix it now rather than waiting.
Once the amended notice of assessment arrives, pay any extra by the due date it shows. If the amendment goes your way, the extra refund is paid to your nominated bank account, though the ATO will first use it to clear any other tax or government debts you owe.
Before you hit Amend: a quick checklist
A few minutes of checking avoids a second round of fixes:
- Wait for your notice of assessment on the original return before amending.
- Check your pre-fill data is now complete, so you catch everything in one go.
- Gather the evidence for any new deduction, such as receipts or a union fee statement, and keep it for five years.
- If the ATO has already written to you about a specific discrepancy, follow the instructions in that letter.
- Still haven't lodged at all? Your own 2025-26 return is due 31 October 2026, so lodge first, then amend later if needed.
FAQ
How long do I have to amend my tax return?
Most individuals have two years, starting from the day after their notice of assessment is sent to them. For example, if your notice of assessment was issued on 5 August 2026, your window starts on 6 August 2026 and runs for two years. People with more complex affairs can have longer.
Can I just lodge a new return to fix a mistake?
No. Don't lodge a second return for the same year. Wait until your original return is processed and your notice of assessment arrives, then use the Amend option in ATO online services through myGov, ask your tax agent to amend it, or send the paper amendment form.
How long does an amendment take to process?
The ATO says an online amendment takes about 20 days to process. Amendment requests made in writing using the paper form can take up to 50 business days.
Will I get a penalty for correcting my own mistake?
If your amendment increases the tax you owe, it's treated as a voluntary disclosure, which generally means lower penalties or none at all compared with the ATO finding the error itself. You may pay a shortfall interest charge on the extra tax, which is usually small if you fix the error promptly.
Run your own numbers