CBTM12003 - Guardian's Allowance: Claiming - Amending claims
Child Benefit & Guardian’s Allowance (Administration) Regulations 2003,regulation 8
Anyone who has made a claim to Guardian’s Allowance may amend it by notifying the appropriate office in writing, as long as the appropriate office (see CBTM12001) is notified before a decision has been made on the claim.
His Majesty’s Revenue & Customs may treat a claim amended in this way as if it had been so amended when it was first made