Questions and Answers
How do I amend my tax return?
I have received a letter from HMRC stating that I may not have told them something and owe tax. I am not sure what to do, please could you help?
Last updated 13 Feb 2026 | First published 1 Feb 2017
By Helen Wood, CA 1 min read
Self-Assessment Tax Returns
HMRC can piece together information on individuals and businesses from submissions via various platforms and through mapping connections across different data sets using its AI systems. This gives HMRC a wider view of your position and therefore they may write to you to highlight a possible mistake or omission in your past tax return submissions.
If you have received a letter from HMRC regarding a submission, firstly check that the letter is genuine. You can check this by looking at HMRC guidance on recent letters they have sent. There are frequent tax scams by criminals and it is important you are vigilant.
The letter from HMRC should detail the action you need to take to appeal or amend your submission. If you are using an accountant, your first step should be to contact them to see if they can resolve the issue on your behalf.
You should only need to submit an amended return if this is what they have requested in their letter. Using your HMRC online services account or a telephone call to HMRC will help you to take the action needed and pay any unpaid tax. Please do ensure that you call HMRC’s main number rather than following any telephone numbers in the letter just in case this is a fraudulent letter.
If you do need to change your tax return and it is within 12 months of the self-assessment deadline (for the 2024/25 tax year the deadline was 31st January 2026 so you have until 31st January 2027) then you can change your return online.
If you need to change your tax return and this deadline has passed, you must write to HMRC to set out the amendments and the effect on your tax position.
Last updated 13 Feb 2026 | First published 1 Feb 2017
This article is intended to inform rather than advise and is based on legislation and practice at the time. Taxpayer’s circumstances do vary and if you feel that the information provided is beneficial it is important that you contact us before implementation. If you take, or do not take action as a result of reading this article, before receiving our written endorsement, we will accept no responsibility for any financial loss incurred.
Helen Wood, CA
Helen is a qualified chartered accountant (CA) and joined TaxAssist in 2025 following three years as a freelance content writer for clients in the tax and accounting publishing sector. Prior to this, She spent 17 years at Big Four and Top 10 accountancy firms. Helen writes clear and helpful articles on tax and accounting for businesses and individuals.
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