Last updated: 16 October 2026
The question
I usually pay about £10,000 a year into my pension. A few years ago I paid in a large one-off contribution after a capital gain, but left it off my tax return, so I overpaid tax. Can I still amend the return?
Amending a return or claiming overpayment relief
You can amend a Self Assessment tax return within 12 months of the 31 January filing deadline. After that, you cannot amend the return itself, but you may be able to claim overpayment relief. This is a formal claim for a refund of tax paid because of an error, made within four years of the end of the tax year concerned.
Time limits
| Tax year | Amend the return by | Overpayment relief claim by |
| 2022/23 | 31 January 2025 (passed) | 5 April 2027 |
| 2023/24 | 31 January 2026 (passed) | 5 April 2028 |
| 2024/25 | 31 January 2027 | 5 April 2029 |
Claims for years earlier than 2022/23 are now out of time.
Missed pension tax relief
Personal pension contributions are paid net of 20% tax, so basic rate relief is added automatically. Higher and additional rate taxpayers must claim the extra relief. Gross contributions extend your basic rate band, which also reduces the tax rate on capital gains.
Worked example
In 2022/23 Karen paid a one-off £40,000 net (£50,000 gross) into her pension after selling shares and forgot to claim the higher rate relief. Extending her basic rate band by £50,000 reduces her income tax by up to £10,000 and can move part of her gain from the higher to the lower CGT rate. Her claim must reach HMRC by 5 April 2027.
How to make an overpayment relief claim
Write to HMRC with:
- your name, address and UTR
- the tax year and a statement that you are claiming overpayment relief under Schedule 1AB of the Taxes Management Act 1970
- the reason you overpaid and how you have worked out the amount
- evidence, such as pension contribution statements
- a declaration that the details are correct and complete, signed by you
When the claim can be refused
HMRC can refuse a claim if the error came from a mistake in how you chose to claim something (such as a missed election), if you could have used another remedy, such as amending the return in time, or if the tax was worked out in line with practice generally accepted at the time.
Other routes to a refund
- PAYE overpayments can be claimed for the previous four tax years through your personal tax account.
- Employees can claim refunds of tax on work expenses for four years.
- Interest is paid on refunds at the repayment rate, currently 2.75%.
Frequently asked questions
Can HMRC look at other errors when I claim?
Yes. HMRC can enquire into the claim and may find underpayments too.
Can I claim if I just did not know about a relief?
Often yes, as long as it is a genuine error and within four years.
Is there any way past the four-year limit?
Only in very limited cases, such as a special relief claim where HMRC is pursuing an old assessment.
How long does HMRC take?
Many claims take several months. Interest helps compensate.
Related: too late for higher rate pension relief?, 40% pension relief and how much tax do I owe.
Talk to Accotax
Want this handled for you? Our team at Accotax can help with tax refund claims. See our tax refund accountants service, or contact us for a free, no-obligation quote.
This page is general guidance based on HMRC rules for the 2026/27 tax year, checked against gov.uk on 16 October 2026. It is not personal advice, so speak to an accountant about your own situation.
