A discovery decision can only be made where a conclusive
decision relating to the entitlement to tax credits is incorrect.
The meaning of “conclusive decision” is defined in the
legislation.
S20(6) defines a conclusive decision on entitlement, or joint
entitlement, as
including a decision made on an appeal against such a decision.
The references to decisions under S18 are all to final decisions made after the end of the year on the entitlement for that year. The S19(3) decision is the decision which you are required to make at the end of every enquiry. S21 allows a revised decision to be made where there has been official error.