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

You must contact HMRC in writing if you need to make changes to your tax return more than 12 months after the Self Assessment deadline. This includes making a change to an earlier tax year.

You’ll also need to write HMRC a letter to:

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

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

What to include

You must include:

  • the tax year you’re correcting
  • why you think you’ve paid too much or little tax
  • how much you think you’ve over or underpaid
  • your signature (no one else can sign on your behalf)

If you’re making an overpayment relief claim, you must also include in your letter:

  • that you’re making a claim for overpayment relief
  • if you’ve previously made an appeal for the same payment
  • a signed declaration saying that the details you’ve given are ‘correct and complete to the best of your information and belief’

You also need to keep evidence that you’ve paid tax through Self Assessment for the relevant period as HMRC may ask for this at a later date.

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

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

View a printable version of the whole guide

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