TCTM09250 - Decision Making: Valid Claims, Conclusive Entitlement and Changes to Decisions
If a change that does not increase the maximum rate, is reported between 6 April and the making of a conclusive decision HMRC must wait until the claimant has made a declaration to implement this change as part of the finalisation process.
A conclusive decision on entitlement cannot however be made until after the s17 notice has been issued. This is because the annual declaration must be in direct response to the s17 notice.
Any change that is ‘designatory’ for example an amendment of address or bank account, can be made at any time.