Mae Deddf Cymru 2014, a gafodd Gydsyniad Brenhinol ar 17 Rhagfyr 2014, yn amlinellu ystod o bwerau trethu a benthyca newydd i Gymru, gan gynnwys datganoli Treth Dir y Dreth Stamp a’r Dreth Dirlenwi yn llawn, benthyca i gefnogi buddsoddi cyfalaf ac i reoli amrywiadau cyllidebol yn sgil datganoli treth, pwerau i greu trethi datganoledig newydd fesul achos (yn amodol ar gytundeb y Cynulliad Cenedlaethol, Tŷ’r Cyffredin a Thŷ’r Arglwyddi), datganoli treth incwm yn rhannol (os bydd pobl Cymru’n cefnogi hynny mewn refferendwm - wedi dweud hynny mae Llywodraeth y DU wedi awgrymu’n ddiweddar y gwaredir y rheidrwydd i wneud hyn), a’r gallu i ddeddfu ar gyfer gweithdrefnau cyllidebol y Cynulliad.  Y dyddiad targed ar gyfer rhoi mwyafrif y pwerau newydd ar waith yw Ebrill 2018.
The Wales Act 2014, which gained Royal Assent on 17 December 2014, sets out a range of new tax and borrowing powers for Wales, including full devolution of Stamp Duty Land Tax and Landfill Tax, borrowing to support capital investment and to manage budgetary fluctuations arising from tax devolution, powers to create new devolved taxes on a case by case basis (subject to the agreement of the National Assembly and both Houses of Parliament), partial devolution of income tax (if supported by the people of Wales in a referendum - although the UK Government has recently indicated that this requirement will be removed), and the ability to legislate for the Assembly's budgetary procedures.  The target date for implementing the majority of the new powers is April 2018.