Change Self Assessment: How to Amend Your Tax Return and Make HMRC Corrections Online

If you need to change self assessment after submitting your tax return, HMRC provides a structured process that allows taxpayers to correct mistakes, update missing information, or revise figures that were previously submitted. A self assessment amendment may be required if you have entered incorrect income details, forgotten to include earnings, or need to adjust figures due to updated financial records.

Understanding how to correct tax return online is important for staying compliant and avoiding penalties. In most cases, you can make HMRC tax return changes through your online personal tax account if you filed your return digitally. However, the rules and time limits must be followed carefully to ensure your amendment is accepted and processed correctly.

When you need to change your Self Assessment

You should change self assessment if you realise there is an error or omission in your submitted return. Common reasons include incorrect income figures, missing expenses, or additional income that was not originally declared. For a broader understanding of how income tax works and how different income types are treated, our personal tax guide provides useful context on tax bands, allowances, and obligations that may affect the figures you need to correct.

A self assessment amendment is also needed if HMRC has issued updated information that affects your tax position or if you discover mistakes after reviewing your submitted return. If you are unsure whether you were originally required to file a self assessment tax return at all, our dedicated guide covers the full eligibility criteria to help you confirm your obligation before making any changes.

How to correct your tax return online

The easiest way to correct tax return online is through the HMRC personal tax account. If you filed your return online, you can log in and make changes directly for the relevant tax year. If you need a refresher on how the original submission process works before making changes, our step-by-step guide on completing your self assessment walks through each stage of the filing process in full detail.

To complete HMRC tax return changes, you must access your Self Assessment section and select the tax year you want to amend. Once inside the return, you can update the necessary sections and resubmit the corrected version.

Steps to amend your Self Assessment online

• Sign in to your HMRC personal tax account using your Government Gateway credentials
• Go to your Self Assessment account section
• Select the tax year you need to amend
• Open your submitted return
• Make the necessary corrections
• Resubmit the updated return to HMRC

It is important to wait at least 72 hours after submitting your original return before making any changes.

Paper returns and software submissions

If you submitted a paper return, you cannot correct tax return online. Instead, you must complete a new set of pages, clearly marking them as an amendment and including your Unique Taxpayer Reference. These must be sent to HMRC at the address used for your original submission.

If you submitted a paper return, you cannot correct tax return online. Instead, you must complete a new set of pages, clearly marking them as an amendment and including your Unique Taxpayer Reference. If you are also unsure whether your filing obligation still applies, our guide on who must send in a tax return covers every category of taxpayer required to file, which can help clarify whether an amendment is needed or whether your return should be withdrawn entirely.

Deadlines for changing your Self Assessment

There are strict deadlines when you change self assessment. Generally, you have up to 12 months after the filing deadline to make amendments online. For example, for most tax years, amendments must be made by 31 January following the end of the tax year. After this deadline, you may need to contact HMRC directly in writing to request changes. One of the most effective ways to give yourself more time to spot and correct errors is filing your tax return early, which leaves a longer window within the amendment period to make corrections before the deadline closes.

For example, for most tax years, amendments must be made by 31 January following the end of the tax year. After this deadline, you may need to contact HMRC directly in writing to request changes.

What happens if you miss the amendment deadline?

A missed amendment deadline may also be a good time to review whether your self assessment obligation still applies going forward. If your circumstances have changed and you no longer meet HMRC’s filing criteria, our guide on what to do if you no longer need to submit a tax return explains how to formally notify HMRC and remove the obligation to file in future years.

In some cases, you may still be able to claim a refund if you have overpaid tax, but this is usually limited to a four-year time window from the end of the relevant tax year.

Conclusion

Knowing how to change self assessment correctly is essential for avoiding errors and ensuring your tax position remains accurate. Whether you are making simple corrections or more detailed updates, using the HMRC online system to correct tax return online is usually the fastest and most efficient method.

By understanding the rules around self assessment amendment and keeping track of deadlines for HMRC tax return changes, you can ensure your tax return remains compliant and up to date.

Expert Guidance on Changing Your Self Assessment With Cigma Accounting in London

Understanding how to change self assessment is important for taxpayers who need to correct errors or update information after submitting a return to HMRC. Cigma Accounting supports clients across Fulham Broadway, including individuals and business owners in Crabtree Lane Area and Fulham Reach, helping them make accurate amendments and stay compliant with HMRC requirements.

A self assessment amendment may be required when income, expenses, or other details have been reported incorrectly. Our team helps clients correct tax return online submissions efficiently and understand the process for HMRC tax return changes, ensuring updates are made accurately and within the permitted timeframe.

Frequently Asked Questions About Changing a Self Assessment Tax Return in the UK

Yes, you can change your Self Assessment tax return after submission if you realise there is an error or missing information. HMRC allows amendments within a specific time limit.

You can change your Self Assessment online by signing into your HMRC account, selecting the relevant tax year, and using the “amend return” option to update your figures.

A Self Assessment amendment is an official correction made to a previously submitted tax return to ensure your income, expenses, or tax calculations are accurate.

You generally have up to 12 months after the Self Assessment filing deadline to make changes to your tax return online with HMRC.

No separate notification is needed if you amend your return online. HMRC automatically updates your record once the amended return is submitted.

Yes. Changing your Self Assessment can increase or reduce your tax liability depending on the corrections made.

Correct Your Tax Return With Confidence and Accuracy

Self assessment amendments allow taxpayers to correct mistakes and update previously submitted returns. Cigma Accounting helps individuals and businesses manage changes accurately, ensuring compliance with HMRC rules and reducing the risk of penalties.

Trusted guidance from London-based accountants, focused on accuracy, clarity, and compliance.