How to amend a Self Assessment tax return
Forgot a CIS statement, missed an expense or used provisional figures? You can correct a filed return. Here's the time limit, how to do it online, and what happens to your bill.
Checked against GOV.UK on 23 October 2026. General information for sole traders in England, Wales and Northern Ireland, not tax advice. Scottish Income Tax rates are different.
The time limit
GOV.UK says you can make a change within 12 months of the Self Assessment deadline:
- 2024/25 return: change it by 31 January 2027.
- 2025/26 return: change it by 31 January 2028.
After that, or for older years, you have to write to HMRC.
Amending online
Wait 72 hours after filing. Then sign in to your HMRC online account, find the return for that year in your Self Assessment account, make the changes and submit it again. If you used commercial software, ask the provider how to amend.
What happens to your bill
Your bill is updated. If you owe more, you'll pay interest from the original due date. If you've overpaid, you can get the difference back. A change can also alter your payments on account.
Common reasons subbies amend
- A CIS statement turned up after filing. Check statements against invoices before filing: see CIS statements.
- Expenses or mileage were missed: see expenses you can claim.
- Provisional figures were used to file on time.
Check the new figures with the January tax bill calculator.
This guide is part of our Self Assessment guides for the self-employed.
Free: The UK Contractor's Cheat Sheet 2026/27
CIS rates, overtime maths, tax dates, mileage, VAT and late payment, on 2 pages. Keep it on your phone or print it for the van.
Frequently asked questions
How long do I have to amend a tax return?
12 months from the filing deadline. For 2024/25 that's 31 January 2027.
How soon after filing can I amend online?
After 72 hours.
Will I pay interest if I owe more?
Yes, from the original payment date.
Sources
- Self Assessment tax returns: corrections – GOV.UK
- Self Assessment tax returns: sending a return – GOV.UK
This guide is general information, not legal, tax or financial advice. Rules and rates change, so check the linked GOV.UK pages for the current position.