within 21 days of either (i) the end of the allowable period to lodge an appeal, or (ii) the end of the formal appeals process, if such an appeal is made
o fewn 21 diwrnod o naill ai (i) diwedd y cyfnod a ganiateir ar gyfer cyflwyno apêl, neu (ii) diwedd y broses apelio ffurfiol, os cyflwynir apêl o’r fath