This part of GOV.UK is being rebuilt – find out what beta means

HMRC internal manual

Self Assessment Manual

Returns: view and amend return: claims to overpayment relief

Where a taxpayer discovers that he has made an error or mistake in his self assessment, he has the right to amend it within 12 months of the statutory filing date. For amendment purposes, the statutory filing date is 31 January following the end of the tax year or 3 months from receipt of a Notice to File by the taxpayer (if it’s a late issue), whichever is the later. Where this time limit has lapsed, he is still entitled to make a claim to ‘overpayment relief’ under Section 1AB TMA 1970; the time limit is 4 years from the end of the relevant tax year.

For more information about claims to ‘overpayment relief’ see business area ‘Repayments’, section ‘Claims made outside a return’ (SAM114000 onwards).