How long does it take for an amendment to process?

Online amendments usually update your tax bill immediately, with your statement reflecting changes within three days. Paper amendments can take longer, often several weeks, for HMRC to process.

Can I amend a return from several years ago?

Yes, but if it's beyond the 12-month amendment window, you must write to HMRC. For older tax years, you might need to claim "overpayment relief" if you've overpaid, which can be done up to four years after the end of the relevant tax year.

What if I made a mistake with my residency status?

If you incorrectly stated your residency status on your Self-Assessment return, you should amend it using the standard process outlined above. This is a change to the information on your return and should be corrected as soon as possible.

How do I view my amended return?

When you amend your return online, the system will show your updated tax bill immediately. Your online Self-Assessment account will reflect the corrected figures and any resulting changes to your tax liability.

Will I be penalised for amending my return?

If you've taken reasonable care in completing your original return and make a minor mistake in good faith, you are unlikely to face a penalty for amending it. HMRC encourages taxpayers to correct errors as soon as they are identified.

How to amend your Self-Assessment return

How to Amend Your Self-Assessment Tax Return

It's common to spot a mistake or realise you've missed something after submitting your Self-Assessment tax return. HMRC allows you to correct these errors, whether it's an incorrect income figure, a forgotten expense, or a change in personal details.

The key is to act within the amendment window. You can make changes to your Self-Assessment tax return within 12 months of the original filing deadline. For example, if you filed your tax return for the 2024/25 tax year by the 31 January 2026 deadline, you have until 31 January 2027 to amend it (figures for illustration – check current rates).

Amending an Online Return

If you filed your Self-Assessment online, the process for amending it is typically quick and easy:

Wait 72 hours: You must wait at least three days (72 hours) after initially filing your return before you can make any changes online.
Sign in: Log in to your HMRC online account (Government Gateway).
Navigate to Self-Assessment: Select "Self Assessment account" from your dashboard.
Access details: Choose "More Self Assessment details".
Find tax return options: From the left-hand menu, select "At a glance", then "Tax return options".
Select the year: Choose the tax year for the return you wish to amend.
Make corrections: Go into the tax return, make the necessary changes, and then re-file it.

Amending a Paper Return

If you submitted your original Self-Assessment tax return on paper, you'll need to send another paper return with the corrections.

Obtain the form: Download the relevant Self-Assessment tax return form (SA100) and any supplementary pages you need, or request them from HMRC.
Mark as amendment: Clearly write "amendment" on each page of the corrected form.
Include details: Ensure your full name and Unique Taxpayer Reference (UTR) are included. Your UTR can be found on previous tax returns or correspondence from HMRC.
Send to HMRC: Post the amended form to the address provided on the Self-Assessment paperwork. If you cannot find it, you can send it to: Self Assessment, HMRC, BX9 1AS.

What Happens After You Amend?

Once you've submitted your amended return, HMRC will process the changes.

Updated Tax Bill: If you amended your return online, your updated tax bill will usually be visible immediately. Your statement will reflect the difference from the old bill and any interest within three days.
Refunds or Additional Payments: Depending on your amendments, you may find you've overpaid tax and are due a refund, or you might owe more tax. If you're due a refund, HMRC will process this. If you owe more, HMRC will inform you of the new payment deadline.

Amending After the Deadline

If you miss the 12-month deadline for amending your return, you can still correct mistakes, but the process changes. You will need to write to HMRC directly.

Your letter should include:

The specific tax year the amendment relates to.
A clear explanation of the information that needs to be corrected.
The reason for the overpayment or underpayment of tax, if applicable.
The exact amount you believe you've overpaid or underpaid.
Your signature in black pen (a printed name is not sufficient).

If you are claiming an overpayment and seeking a refund, you should also state this in your letter, provide evidence of the tax paid, confirm you haven't claimed this refund before, and indicate how you wish to receive the refund (e.g., bank transfer).

Common mistakes

Missing the 12-month deadline: Failing to amend within 12 months of the original filing deadline makes the process more complex, requiring a letter to HMRC.
Not waiting 72 hours: Trying to amend an online return immediately after filing will not work; you must wait three days.
Assuming HMRC will correct minor errors: While HMRC may correct obvious clerical errors, it's your responsibility to ensure your return is accurate.
Not keeping records: Always keep detailed records of your income and expenses to make any future amendments easier.

Frequently asked questions

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