How do I Amend my Tax Return after Filing it?
When errors occur in your self assessment tax return, addressing them promptly demonstrates your commitment to compliance and helps avoid potential complications with HMRC.
The process for amending your tax return varies depending on when you discover the error or omission.
Whether it’s within days of submission or years later, HMRC gives you a pathway to rectify mistakes.
Remember that mistakes happen – what matters is taking appropriate action to correct them by making an amendment.
Being proactive about amendments not only ensures you pay the correct amount of tax but also prevents potential investigations that might arise from unaddressed discrepancies.
There are a number of reasons why you might need to change your already submitted tax return which include claiming for expenses or reliefs resulting in a refund of tax.
Our guide will walk you through the process of amending your self assessment tax return online, or by post and covers the overpayment relief claim process if you are due a tax refund.
When can I amend my tax return?
Various circumstances might mean you need to make a change(s) to your original self assessment tax return submission.
Personal details might need updating, financial information could require correction or missing information input.
Here are several typical scenarios where amendments become necessary:
- Relief claims might be necessary if you’ve identified eligible deductions or tax allowances after submission.
Tax relief opportunities are sometimes discovered retrospectively, and amending your return allows you to benefit from these entitlements. Depending on the timescale you may need to claim your deductions and/or allowances via an overpayment relief claim which we discuss later in this article.
- Personal information updates often require attention when your contact details change during the tax year.
If you’ve relocated or legally changed your name, ensuring HMRC has your current information is crucial for effective communication regarding your tax affairs.
- Financial data corrections become essential when you notice discrepancies in reported income figures.
These could include incorrect earnings, overlooked income streams, or miscalculated expenses.
It’s worth noting that not all amendments will affect your tax bill. Updates to personal information typically won’t alter your financial obligations, whereas corrections to income figures or expense claims will likely impact your tax liability.
Timeframes for making tax return amendments
Understanding the deadlines for modifying your tax return is essential to ensure you can make necessary corrections without complications.
HMRC provides a specific window during which online amendments are relatively straightforward providing ample opportunity to identify and correct most errors.
Online tax returns:
The standard timeframe allows modifications within one year of the original filing deadline. For instance, if your tax return was due on 31 January 2023, you have until 31 January 2024 to make amendments through the standard process.
For paper returns:
The same one-year deadline applies, though the process differs slightly from online submissions. Regardless of your filing method, acting promptly once you discover an error is advisable to avoid potential complications or penalties.
Amendments after one year deadline:
If you miss the twelve months window, don’t panic – amendments remain possible, though through a different process called an overpayment relief claim that requires direct communication with HMRC.
These late corrections may require additional documentation and explanation, but the pathway to rectification remains open.
Online tax return amendment process
For those who submitted their self assessment electronically, the amendment process is straightforward and can be completed entirely online.
This digital approach offers convenience and typically results in faster processing of your corrections.
Before beginning, note that you must wait approximately 72 hours after your original submission before the system will allow amendments.
This brief delay enables HMRC’s systems to fully process your initial return.
To modify your online submission, follow these steps:
- Access your HMRC online account using your government gateway credentials.
- Navigate to the self assessment section within your account.
- Select “More self assessment details” from the available options.
- Choose “At a glance” from the menu panel.
- Click on “Tax return options” to view your submission history.
- Select the relevant tax year that requires amendment.
- Open the appropriate return, make your necessary changes.
- Resubmit the corrected version to HMRC.
HMRC’s self assessment system will automatically calculate any changes to your tax liability based on your amendments and update your SA record to show any additional tax liability or refunds due.
Paper return amendment process
If you originally submitted your Self Assessment on paper, you’ll need to follow a different procedure to make corrections. While slightly more time-consuming than the online method, the paper amendment process remains straightforward.
To amend a paper submission, you’ll need to:
- Obtain a new self assessment form – either download it from the HMRC website or request a physical copy by contacting their helpline.
- Clearly mark “amendment” on each page of the new form to distinguish it from an original submission.
- Include your complete name and unique taxpayer reference (UTR) on all pages.
- Complete the entire form with all information, including both correct and unchanged details.
- Submit the amended return to the appropriate HMRC address.
When sending your amended paper return, use the address printed on the form itself.
If this information isn’t visible, send your documents to the general self assessment address: Self Assessment, HMRC, BX9 1AS.
Tax return amendments after the 12 months deadline
Discovering errors beyond the standard amendment window requires a different approach. While the one-year deadline is important, HMRC still provides a way for correcting historical returns.
When the standard amendment period has elapsed, you’ll need to write directly to HMRC explaining the situation. Your correspondence should include:
- Your complete personal details (full name, address, national insurance number, and UTR).
- Specific tax year requiring correction.
- Detailed explanation of the error and necessary amendments.
- Supporting documentation evidencing the correct information.
- Calculation of tax overpaid or underpaid as a result.
- Your signature in ink (digital signatures aren’t accepted for this purpose).
- If your amendment would result in a tax refund, additional information becomes necessary.
Overpayment relief claim for self assessment tax refunds
If you are amending your tax return to claim back a refund of tax outside of the 12 month threshold you should write to HMRC making what’s known as an “overpayment relief” claim.
You must clearly state that you’re claiming a refund of tax, provide evidence of previous repayments, confirm this isn’t a duplicate claim, and specify your preferred refund method.
HMRC typically allows overpayment relief claims within four years from the end of the relevant tax year, providing a significant window to claim back a refund through self assessment.
Example HMRC overpayment relief claim letter:
Below is an example of how to structure an overpayment relief claim letter that has the details HMRC needs to review your claim.
PAYE Self-Assessment
HM Revenue and Customs
BX9 1AS
[Your Full Name and Address]
[Your Contact Number]
[Your Email Address]
[Date]
RE: Claim for Overpayment Relief
Dear Sir/Madam,
Overpayment Relief Claim
I am writing to make a claim for overpayment relief under Schedule 1AB of the Taxes Management Act 1970.
Claim Details:
Tax Year/Accounting Period: [Enter tax year e.g., 2024/25 or specific accounting period]
National Insurance Number: [Your NI number]
Unique Taxpayer Reference (UTR): [Your unique tax reference number]
Amount of Overpayment: £[Enter amount]
Grounds for Overpayment:
I believe I have overpaid tax for the above period due to the following reason(s):
Provide a clear and detailed explanation of why you believe you have overpaid. For example:
- Error in calculating income
- Expenses or allowances not claimed
- Duplicate payment made
Supporting Evidence:
I have enclosed the following documentation to support my claim:
[List all relevant documents you are attaching e.g., P60, P45, mileage records, accommodation receipts, bank statements, etc.]
Previous Appeals:
I confirm that I [have/have not] previously made an appeal in connection with this payment or assessment.
[If you have made a previous appeal, provide details here]
Declaration:
I declare that the information I have given on this claim is correct and complete to the best of my knowledge and belief.
Payment Details:
If my claim is successful, please make the repayment to:
Account Name: [Your account name]
Account Number: [Your account number]
Sort Code: [Your sort code]
Yours faithfully,
[Your signature in ink]
[Your full name printed]
[Date in ink]
Keeping a copy of your letter and other attachments is recommended just in case you need to refer to it or send a copy to HMRC in the future.
HMRC will review your overpayment relief claim and notify you in writing of their decision. Any tax refund calculated from a successful overpayment relief claim will be applied to your self assessment record as a freestanding credit which you can reclaim.
Processing times and tax bill updates
After submitting amendments, understanding when and how your tax bill will update helps manage expectations and financial planning.
Processing times vary depending on your submission method and the complexity of your changes.
For online amendments, your revised tax calculation should appear in your HMRC account within approximately three days.
This updated statement will clearly show the difference between your original and amended submissions, highlighting any additional tax due or refunds owed.
Paper amendments typically take longer to process because it takes longer for HMRC to process physical documents.
Updated tax calculations usually arrive within four weeks of processing and will either show if your amendments result in an additional tax liability or if you’re due a refund.
