--- title: "How to Correct a Self Assessment Tax Return After Submission | TCK Accounting" description: "How to amend a UK Self Assessment tax return after filing, including the 72-hour online wait and the 12-month correction window." canonical: "https://www.tckaccounting.co.uk/blog/how-to-correct-a-self-assessment-tax-return-after-submission" last_updated: "2026-01-27T11:52:33.895Z" --- # How to Correct a Self Assessment Tax Return After Submission PublishedTuesday, 27 January 2026 ![A person at a desk reviewing documents and using a computer in a calm home office environment.](/_next/image?url=%2Fapi%2Fmedia%2Ffile%2Fcorrecting-return-after-filing-hero.png%3Fv%3D1769514404538&w=1536&q=75&dpl=dpl_HkjxAMLz8SoKDEaYz6gDcGJLMf1v) ## Key takeaways - You can amend a Self Assessment tax return **within 12 months of the Self Assessment deadline**. - If you filed **online**, you must **wait 72 hours (3 days)** after submission before you can amend it. - You can amend by **sending another paper return** (within the correction time limit). - If you miss the amendment deadline (or need to change an earlier tax year), you’ll need to **write to HMRC**. ## Why you might need to correct a return It’s common to spot an issue after you’ve filed — for example, a figure entered incorrectly or something missed. When you amend your return, your Self Assessment bill will be updated based on the corrected information. This may mean you owe more tax, or you may be due a refund. > Note: Amending a return is different from filing late — it’s about correcting what you’ve already submitted. ## What you’ll need Before you start, make sure you have: - The **tax year** you need to correct. - Access to your **Self Assessment online account** (if you’re amending online). - Your **Unique Taxpayer Reference (UTR)** if you’re sending paper corrections (your UTR is on previous tax returns or letters from HMRC). ## How long you have to make a correction You can correct a tax return **within 12 months of the Self Assessment deadline**, either: - **online**, or - by **sending another paper return**. ### Worked example (using an HMRC example) For the **2023 to 2024 tax year**, you’ll usually need to change your return by **31 January 2026**. ## Method 1: Amend an online Self Assessment return (step-by-step) You must **wait 3 days (72 hours)** after filing before you can update an online return. ### Steps 1. **Sign in** to your account. 2. From **“Your tax account”**, choose **“Self Assessment account”**. 3. Choose **“More Self Assessment details”**. 4. Choose **“At a glance”** from the left-hand menu. 5. Choose **“Tax return options”**. 6. Choose the **tax year** for the return you want to amend. 7. Open the return, **make the corrections**, then **file it again**. ## Method 2: Amend by paper (within the time limit) If you’re correcting by paper, HMRC’s guidance is to send the corrected pages and clearly mark them as an amendment. ### Steps 1. Get the return and any supplementary pages you need. 2. Complete the **corrected pages**. 3. On **each corrected page**, write **“amendment”**. 4. Include your **name** and **UTR**. 5. Send the corrected pages to the **address on your Self Assessment paperwork**. If you cannot find the address, HMRC’s guidance says you can send corrections to: > Self Assessment > HM Revenue and Customs > BX9 1AS ## What happens after you amend ### If you amend online - You’ll see your **amended bill straight away**. - Within **3 days**, your statement will also show: - the **difference** from the old bill (so you can see whether you owe more or less) - any **interest** ### If you amend by paper HMRC will send you an **updated bill**. ## Pitfalls and troubleshooting ### “I submitted online and can’t amend it yet” If it’s been less than **72 hours** since you filed, you’ll need to wait before the online amendment option becomes available. ### “It’s been more than 12 months since the Self Assessment deadline” If you miss the deadline — or if you need to change a return from an **earlier tax year** — HMRC’s guidance is that you’ll need to **write to HMRC**. HMRC says your letter must include: - the **tax year** you’re correcting - **why** you think you’ve paid too much or too little tax - **how much** you think you’ve overpaid or underpaid - your **signature** (no one else can sign on your behalf) If you’re making an **overpayment relief** claim, HMRC also requires additional information in your letter, including a signed declaration. ### “I used commercial software” HMRC’s guidance is to contact your **software provider** for help correcting your return. If your software cannot make corrections, you’ll need to contact HMRC. ## Quick checklist - Confirm you’re within **12 months of the Self Assessment deadline** for the return. - If amending online, check it’s been at least **72 hours** since submission. - Select the right **tax year** and make the corrections. - Re-file the amended return (online). - If sending paper corrections, write **“amendment”** on each corrected page and include your **name and UTR**. - If you’re outside the amendment window, prepare a letter to HMRC including all required details. ## Summary If you need to correct a Self Assessment tax return after submission, you normally have **12 months from the Self Assessment deadline** to do it. Online amendments require a **72-hour wait** after filing, while paper corrections can be made by sending updated pages marked as an **amendment** (within the time limit). If you’re outside the amendment window or changing an earlier tax year, HMRC’s guidance is to **write to them** with the required information. 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