Predecessor taxes’ currently refers to Stamp Duty Land Tax and Landfill Tax – the UK equivalents for the taxes that are now devolved in Wales.
Ar hyn o bryd, mae 'trethi rhagflaenol' yn cyfeirio at Dreth Dir y Dreth Stamp a’r Dreth Tirlenwi – trethi cyfatebol y DU i’r trethi sydd bellach wedi'u datganoli yng Nghymru.