If you’re unable to file or pay your tax to us on time because of your circumstances, tell us as soon as possible, and before the return or payment of tax is due.
Os na allwch ffeilio neu dalu eich treth i ni ar amser oherwydd eich amgylchiadau, dywedwch wrthym cyn gynted â phosibl, a chyn i'r ffurflen dreth neu’r taliad fod yn daladwy.