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HMRC internal manual

Self Assessment: the legal framework

Claims, Elections and Notices: amendments of claims

HMRC is able to correct the claim during initial processing

Para 3(1)(a), Schedule 1A

An officer of the Board may ‘correct’ obvious mistakes or errors in a claim. Any such amendment must be made before the end of the period of nine months beginning with the day on which the claim is made.

The claimant may make amendments providing the claim is not under enquiry

Para 3(1)(b) & (2), Schedule 1A

Similarly, a claimant may amend a claim at any time before the end of the 12-month period beginning with the day on which it is made.

But neither the claimant nor an officer of the Board can amend a claim while it is under enquiry.