How far back can you amend a tax return in the UK

Unfortunately, not everyone gets it right on the first try and sometimes you need to amend your HMRC tax return after submitting it.

This often brings about the common question: Can I amend my HMRC tax return after submitting it - and is there a time limit? In short, yes you can. Here is a quick rundown of what you need to know about amending your HMRC tax return outside the time limit.

Deadline for amending your return

According to stipulations from the HMRC, you have up to 12 months from the Self Assessment deadline to file any corrections or changes to your tax return. The Self Assessment deadline is usually set as 31st January each year.

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Amending your tax return outside the time limit

If the 12 month mark has passed and you need to make an amendment to your tax return, you can still do so but the process will differ. In this case, you will need to contact the HMRC’s Self Assessment department to explain your error. If you want to claim a refund for an overpayment, you can do so up to 4 years after the end of the tax year in question. 

Reasons for potential tax return changes

While it may seem daunting once realised, these are all HMRC-validated reasons to amend your tax return.

• A typo or spelling error has been made on your tax return
• Your HMRC tax return contains an error that will impact your tax calculations
• You’ve forgotten to add something, such as an expense
• Your name or address has changed during the same year as your tax filing
• You have realised that you paid too much tax and want to claim for overpayment relief from HMRC (you can find more information about this below). 

How to amend your tax return based on your submission method

You can make amendments to your tax return in several ways and this would depend largely on the method you chose to submit your HMRC tax return in the first place.

Via HMRC Portal online

If you have filed your Self Assessment tax return online via the HMRC website, you will need to wait at least 3 days after your submission before you can make any changes. To make changes to your tax return on the HMRC Portal online.

1. Sign into your Government Gateway account.
2. Select ‘Your tax account’ and then ‘Self Assessment account.’
3. Select ‘More Self Assessment details’ followed by ‘At a glance’.
4. You should then be able to choose the tax year you wish to amend under ‘Tax return options’.
5. Once selected, you will be able to make changes to the tax return and file it again.

Via post

Alternatively, you can make amendments to your tax return via post. You will need to call the HMRC helpline and request form SA100 for your main Self Assessment tax return. All other supplementary pages can be downloaded.

To make your amendment, label each corrected page with the term ‘amendment’ and your unique identification number (UTR) and your name. You will need to send the corrected pages to:

Self Assessment
HM Revenue and Customs
BX9 1AS

Via 3rd party software

If you submitted your tax return through a 3rd party software, you will need to speak to your software provider to ascertain the next steps in correcting a tax return. If  your software does not allow for any changes/amendments to be made, speak to your software’s account manager. 

What to include on your amendment

If you have missed the deadline to make an amendment or would like to make changes to a previous tax year, you will have to contact HMRC in writing. In this case, it is recommended that you include the following:

• Information on the relevant tax period you are amending
• Details on the amount you think you have overpaid/underpaid
• Reasons for your amendment
• Proof you have paid your tax through Self Assessment (if you are making a claim for overpayment)
• How you would like to be repaid
• Signed declaration testifying to the accuracy and validity of the information you have provided

When can you expect to see the changes reflected in the tax bill 

Your tax bill will change once you have made the amendments to your tax return. The time between correcting your error and the change in your tax bill will depend on how you made your amendment.

Online
If you filed your Self Assessment and made your amendments online, the changes in your tax bill should be reflected within 3 working days. If you owe additional tax after the recalculations, you will be able to see a new deadline to pay any tax owed. On the other hand, if you are owed a refund you should be able to request a refund for your overpayment via your online HMRC account.

Via post
If your amendments were done via post, the HMRC will contact you within 4 weeks with an updated tax bill and instructions on your next steps. If you are owed a refund for overpayment, you will need to confirm your bank details. 

Claiming for overpayment relief

If you believe an error on your Self Assessment tax return form has led to you paying too much tax, you may be able to claim for overpayment relief from HMRC.

You are able to claim a refund up to 4 years after the end of the tax year in question.

To do this, you will need to make an overpayment claim in writing to the HMRC and should include the following details:

• The tax/accounting year to which the claim for overpayment relief claim relates
• Details of the amount believed to be overpaid
• Confirmation that you are claiming for overpayment relief
• Details on how you would like to receive your refund for the overpayment (bank details, sort code)
• Signed declaration confirming the provided information is correct and true to your knowledge
• Proof of payment for the tax return in question

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