Ers cyhoeddi rhestr fer o bedwar syniad newydd am drethi wrth ochr y Gyllideb Ddrafft ym mis Hydref, bu Llywodraeth Cymru yn edrych ar yr achos dros bob un ohonynt.
Since announcing a shortlist of 4 new tax ideas alongside the draft Budget in October, the Welsh Government has been examining the case for each of these.