Yes — HMRC allows you to amend your Self Assessment tax return after submission, provided you do so within the permitted time limits.
Many taxpayers discover mistakes after filing, such as missing income, forgotten expenses, or incorrect figures. The good news is that these errors can usually be corrected — and in some cases may even result in a tax refund.
At Vales Tax Return, we regularly help individuals amend Self Assessment tax returns accurately and safely, avoiding HMRC penalties and unnecessary stress.
When Can You Amend a Self Assessment Tax Return?
You can amend your tax return up to 12 months after the statutory filing deadline.
Example
- Tax year: 2022/23
- Filing deadline: 31 January 2024
- Amendment deadline: 31 January 2025
As long as your original return was submitted on time, HMRC will allow amendments within this window.
What If I Miss the Amendment Deadline?
If the 12-month amendment window has passed, you cannot amend your return online.
Instead, you must contact HMRC directly — usually by letter — and request a correction. This is known as a claim for overpayment relief or a correction request.
HMRC may allow changes up to four years after the end of the tax year, but the process is more detailed and requires supporting evidence.
What Information Does HMRC Require for Late Amendments?
When requesting changes outside the online amendment window, HMRC typically requires:
- The tax year being corrected
- The difference in tax (overpaid or underpaid)
- A clear explanation of why the return is being amended
If you are claiming a refund, you must also confirm:
- That you are making a formal overpayment relief claim
- That you have not previously claimed for the same issue
- Evidence that the original tax was paid
- Your repayment details
- A signed declaration confirming accuracy
Errors or missing details can delay or invalidate the claim.
How Do I Amend a Recent Self Assessment Tax Return?
If you are still within the amendment window, you can:
- Amend your return via the HMRC online portal, or
- Ask your accountant to resubmit the corrected return on your behalf
When submitting an amended return, HMRC requires:
- A brief explanation of what has changed and why
Once submitted, HMRC will usually issue:
- An updated tax calculation within a few weeks
- Either a revised payment deadline or refund instructions
Common Reasons for Amending a Tax Return
Tax returns are commonly amended due to:
- Forgotten income (freelance, rental, dividends)
- Missed allowable expenses
- Incorrect figures or calculations
- Changes to employment details
- Incorrect claims or reliefs
- Errors in residency or tax status
Correcting mistakes promptly reduces the risk of HMRC enquiries and penalties.
Will HMRC Penalise Me for Amending My Return?
Amending a return does not automatically trigger a penalty.
Penalties usually arise if:
- Errors are deliberate
- Underpaid tax is not disclosed
- HMRC identifies the error before you do
Voluntarily correcting mistakes is viewed positively by HMRC.
How Vales Tax Return Can Help
We assist clients with:
Reviewing submitted tax returns- Identifying errors and missed reliefs
- Preparing and submitting amended returns
- Overpayment relief claims
- HMRC correspondence and support
Whether you filed yourself or through another provider, we ensure your amended return is accurate, compliant, and optimised.
Need to Amend Your Self Assessment Tax Return?
If you think something doesn’t look right — don’t ignore it.
Get expert help amending your tax return Recover overpaid tax where possible Avoid HMRC penalties and future issues
