Claims are made in tax self-assessments and are checked by the Welsh Revenue Authority (WRA), which has responsibility for ensuring taxpayers pay the correct amount of tax.
Caiff ACC ei archwilio gan Archwilio Cymru sydd, ar ran Archwilydd Cyffredinol Cymru, yn gyfrifol am adolygu ac archwilio rheolaethau ariannol a dibynadwyedd y cyfrifon ariannol.