the end of the ‘appeal period’ (see below) for a decision which corrects the inaccuracy or understatement (such as a decision to make a WRA assessment), or
ar ddiwedd y ‘cyfnod apelio’ (gweler isod) am benderfyniad sy’n cywiro’r anghywirdeb neu’r tanddatganiad (fel penderfyniad i gynnal asesiad ACC), neu