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HMRC internal manual

Self Assessment Claims Manual

Unsuccessful Attempts to Make a Claim or Election: Unsatisfactory Claims Made Outside a Return

See SACM10010 for what is an unsatisfactory claim.

Where the claim is made outside a return, you should explain to the taxpayer that they have not made a valid claim and what they need to do to make such a claim.

If you are writing to the taxpayer to invite a valid claim after or just before the end of the time limit for making the claim you should give the taxpayer a reasonable extension of time to send you a proper claim. The 14 days that we use when we send back unsatisfactory ITSA return forms would usually be appropriate. If there are particular circumstances that mean 14 days would be insufficient (for example, the customer being overseas) then you can allow a longer reasonable amount of time.