This is due to the small number of landfill operators who had already submitted returns and paid before the end of June (most of them submitted and paid in July).
Mae oherwydd nifer fechan y darparwyr a oedd eisoes wedi cyflwyno ffurflenni ac wedi talu cyn diwedd mis Mehefin (cyflwynodd a thalodd y rhan fwyaf ohonynt ym mis Gorffennaf).