Caiffdau Fil Trethieu cyflwyno i sefydlu'r ddwy dreth i’w datganoli i Gymru ym mis Ebrill 2018; sef y dreth trafodiadau tir, a fydd yn disodli treth dir y dreth stamp  (SDLT) bresennol, a threth gwarediadau tirlenwi i Gymru, a fydd yn disodli’r dreth dirlenwi bresennol.
TwoTax Billswill be introduced to establish the two taxes to be devolved to Wales in April 2018; a land transaction tax, which will replace the current stamp duty land tax (SDLT), and a landfill disposals tax for Wales, which will replace the current landfill tax.