Time limits
| Tax year | Online filing deadline | Amend by |
|---|---|---|
| 2024-25 | 31 January 2026 | 31 January 2027 |
| 2025-26 | 31 January 2027 | 31 January 2028 |
After the deadline to amend, you cannot change the return itself. If you paid too much, you can claim overpayment relief in writing within 4 years of the end of the tax year. If you underpaid, tell HMRC.
How to amend in Self Assessment Software
- Open the accepted returnOpen the return for the tax year. The confirmation page shows Submission accepted.
- Choose Start amendmentConfirm: you can edit the return and resubmit it to HMRC as an amendment. The desk shows Amendment in progress.
- Correct the figuresChange the boxes that were wrong. The calculation updates as you go.
- Review and approveSend the amended return for review and approve it. Accountants: any earlier client approval is cancelled, so email the client again.
- Submit the amendmentChoose Submit amended return to HMRC. When accepted, the status shows the amendment as accepted.
Amend or correct?
| Return status | What to do |
|---|---|
| Accepted by HMRC | Start an amendment, as above |
| Rejected by HMRC | Not filed. Unlock, correct and resubmit. See HMRC rejected my return |
| Still checking | Wait, then Check with HMRC |
What happens after you amend
HMRC updates your tax bill. If you owe more, pay the extra as soon as possible: interest runs from the original due date. If you overpaid, HMRC repays or credits you.
Your payments on account for the next year may change too. Download your tax year overview again once HMRC has processed the amendment, especially if a lender needs it.
If the online amendment window has closed, the filing desk tells you to send the amendment on paper.
Still stuck?
- No Start amendment button? Only an accepted return can be amended.
- Only an accepted return can be amended. If the return was rejected, unlock and resubmit it instead.
- Amending close to a deadline? Pay any extra tax first to limit interest.
Still not sorted? Contact us and tell us the page, the tax year and any message you see.
Questions answered
How long do I have to amend my tax return?
12 months from the 31 January filing deadline. For the 2025-26 return that is 31 January 2028.
Can I amend a return I filed with software?
Yes. Amend it in the same software. In Self Assessment Software choose Start amendment on the accepted return.
Do I pay again to amend?
No. Amendments for the same tax year are included.
Will I get a penalty for amending?
Correcting an honest mistake is not penalised in itself, but you pay interest on any extra tax from the original due date. Careless or deliberate errors can lead to penalties.
What if I miss the deadline to amend?
Write to HMRC. If you paid too much, you can claim overpayment relief within 4 years of the end of the tax year.
Official sources
These guides explain how HMRC's rules apply in Self Assessment Software. Check GOV.UK for your own circumstances.