Cafodd cyfraddau treth incwm Cymru eu cyflwyno ar 6 Ebrill eleni. I baratoi ar gyfer hynny, bu Cyllid a Thollau Ei Mawrhydi (CThEM) yn gweithio gyda chyflogwyr a darparwyr gwasanaethau’r gyflogres i nodi’r trethdalwyr sy’n byw yng Nghymru  y dylid neilltuo’r cod treth ‘C’ newydd iddynt. Yna, fe roddodd CThEM y codau treth newydd, ynghyd â’r canllawiau technegol a’r data profi sy’n cyd-fynd a nhw, i gyflogwyr cyn 6 Ebrill er mwyn gwneud yn siŵr bod yr holl wybodaeth ganddynt i roi’r newid ar waith.
Welsh rates of income tax (WRIT) were introduced on 6 April this year. In readiness for this, HMRC worked with employers and payroll providers and identified income tax payers living in Wales to whom the new ‘C’ tax code should be assigned. HMRC then issued the new tax codes and the accompanying technical guidance and test data to employers prior to 6 April, to ensure they had all of the information needed to implement the change.