Self Assessment tax returns

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If you need to change your return

You can make a change to a tax return after you filed it, for example because you made a mistake.

Your bill will be updated based on what you report. You may have to pay more tax or be able to claim a refund.

Updating your tax return

You can correct a tax return within 12 months of the Self Assessment deadline, online or by sending another paper return.

Example

For the 2023 to 2024 tax year, you’ll usually need to change your return by 31 January 2026.

If you miss the deadline or if you need to make a change to a return from an earlier tax year, you’ll need to write to HMRC.

Online tax returns

You must wait 3 days (72 hours) after filing before updating your return.

  1. Sign in to your account.

  2. From ‘Your tax account’, choose ’Self Assessment account’.

  3. Choose ‘More Self Assessment details’.

  4. Choose ‘At a glance’ from the left-hand menu.

  5. Choose ‘Tax return options’.

  6. Choose the tax year for the return you want to amend.

  7. Go into the tax return, make the corrections and file it again.

Paper tax returns

For the main Self Assessment tax return you can:

You can download all other forms and supplementary pages.

You then need to send the corrected pages to the address on your Self Assessment paperwork.

Write ‘amendment’ on each page and include your name and Unique Taxpayer Reference (UTR) - this is on previous tax returns or letters from HMRC.

If you cannot find the address, you can send your corrections to:

Self Assessment
HM Revenue and Customs
BX9 1AS

If you used commercial software

Contact the software provider for help correcting your tax return. Contact HMRC if your software is not able to make corrections.

Changes to your bill

You’ll see your amended bill straight away if you updated your tax return online. Within 3 days, your statement will also show:

  • the difference from the old one, so you can see whether you owe more or less tax
  • any interest

To view this, sign in to your account and choose ‘View statements’ from the left-hand menu.

If you’re owed tax

You may be able to claim a tax refund.

If you need to pay more tax

Your updated bill will also show:

If you sent an updated paper return

HMRC will send you an updated bill. You can check when you can expect a reply from HMRC.

They’ll pay any refund directly into your bank account, as long as you include your bank details on your tax return.

If you’ve missed the deadline to change your return

If your return is incorrect and it’s more than 12 months after the Self Assessment deadline you’ll need to write to HMRC to:

  • report income you did not include in your tax return
  • claim overpayment relief, if you think you’ve overpaid tax

Reporting income you did not include in your tax return

You should contact HMRC in writing and include:

  • the tax year you’re correcting
  • why you think you’ve paid too little tax
  • how much you think you’ve underpaid
  • your signature

HMRC will review your information, and contact you if they need more details. The amount you owe may be updated based on what you tell them.

Claiming overpayment relief

You can claim overpayment relief up to 4 years after the end of the tax year it relates to.

You should contact HMRC in writing, you must include:

  • that you’re making a claim for overpayment relief
  • the tax year for which you think you paid too much tax
  • why you think you’ve paid too much tax
  • how much you think you’ve overpaid
  • if you have, or have not, previously made an appeal for the same payment

If you do not include all of this information your claim will be rejected.

You must include a declaration saying the details you have given are ‘correct and complete to the best of your information and belief’. The declaration must be signed by:

  • you, if you are claiming for yourself
  • a company officer (for example a director, shadow director, company secretary or manager of the company) if the claim is for a limited company

No one else, including a tax agent, can sign on your behalf.

You can also tell HMRC how you want to be repaid in your letter.

HMRC will review your information, and contact you if they need more details. The amount you owe may be updated based on what you tell them.

You need to keep evidence of the tax you think has been overpaid for the relevant period as HMRC may ask for this later.

View a printable version of the whole guide

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