Filing a 60-day CGT return under time pressure means errors happen. A figure copied from the wrong document, an improvement receipt found after filing, a joint ownership percentage applied incorrectly. All of these can be corrected.
You can amend a 60-day return
HMRC allows amendments to 60-day CGT returns. The amendment window is 12 months from the 31 January following the end of the tax year in which the disposal was made.
For a property that completed in July 2025 (tax year 2025-26), the amendment deadline is 31 January 2028. That gives you more time than most sellers realise.
How to amend
Log in to HMRC's CGT on UK property service with your Government Gateway credentials. Find the return you submitted and select the option to amend it. You enter the corrected figures, and HMRC recalculates the tax.
If you used an agent (such as LetsFile), you can ask them to amend on your behalf, provided the authorisation is still active.
What happens to tax already paid
If the amendment reduces your CGT liability, HMRC will repay the difference. Repayments are usually made to the bank account you provided at the time of payment, though HMRC may ask you to confirm payment details.
If the amendment increases your liability, additional tax is due from the date it was originally payable. HMRC charges interest on late payments, so an amendment that increases the CGT due will also result in an interest charge for the period between the original deadline and the date of additional payment.
Correcting through the SA100
The annual self-assessment return (SA100) includes a reconciliation of CGT paid via the 60-day return. If your total CGT liability for the tax year changes on the SA100 because your income puts more or less of the gain into the higher-rate band, any difference is collected or repaid via the self-assessment process.
This is a common route for correcting mistakes that only become apparent once the full tax year picture is known. You do not necessarily need to amend the 60-day return itself if the SA100 will pick up the correction.
What cannot be corrected through amendment
If HMRC opens an enquiry into your return, you cannot amend it while the enquiry is open. For details on what triggers an enquiry and how to respond, see our guide to HMRC enquiries into property CGT returns. HMRC has the power to correct the return itself through the enquiry process, and any adjustments will be made as part of the enquiry settlement.
Once the amendment window has passed (12 months from 31 January following the tax year), corrections can only be made through a formal overpayment relief claim, which has stricter time limits and requires evidence that the original assessment was genuinely wrong.
The most common reasons to amend
In practice, most amendments fall into a small number of categories:
- A capital improvement receipt found after filing. This reduces the gain and the tax.
- A solicitor's fee figure that was estimated at filing and later confirmed as a different amount.
- An error in the PRR fraction. This is common where the period of occupation was calculated from memory rather than from records.
- An incorrect apportionment in a joint ownership case, where one co-owner filed with the wrong percentage.
Should you amend or wait for the SA100?
If the error is material (say, several thousand pounds of gain that was wrongly included or excluded), amend the 60-day return directly. The amendment creates a clear paper trail and ensures the figures on the 60-day return match what eventually appears on the SA100.
For minor discrepancies, it is sometimes easier to let the SA100 reconciliation process pick up the difference, particularly if you are already within self-assessment and file an annual return. Discuss the options with your accountant.
Late filing versus amended filing
An amendment is not the same as a late return. If you never filed the original return at all, you cannot treat an amendment as a way to file late. A late return is a late return, and penalties apply from day one of the missed deadline. Our guide on whether you need to file when no tax is due can help you determine whether a return was required in the first place. The amendment process only applies once an initial return has been submitted.
LetsFile reviews the figures in your completed return before submission. If we identify an error after filing, we will advise you on whether to amend and, if authorisation is still active, handle the amendment at no additional charge.