How to Fix Mistakes on Your Tax Return (Without Panicking)
If the 12-month amendment window has closed, you can’t change your return through your account. But you’re not stuck.
You can write to HMRC and ask them to make a correction. In your letter, include:
If the correction means you paid too much tax, HMRC might issue a refund. But they are not obliged to. You have four years from the end of the tax year to claim back overpaid tax.
For example, to claim a refund for the 2021 to 2022 tax year, you must contact HMRC by 5 April 2026.
