Unsuccessful Attempts to Make a Claim or Election: Unsatisfactory Claims Made In a Return
See SACM10010 for what is an unsatisfactory claim.
If the unsatisfactory claim is made in a return then it may be possible to correct it as an obvious error. It the taxpayer rejects the correction, or one is not possible, the claim can be challenged by opening an enquiry into the return under TMA70/S9A or 12AC. Although they have not made a claim they will have delivered a valid return and the correct way to challenge a figure in that return is by opening an enquiry.