Yn fy Natganiad Ysgrifenedig ar 9 Mawrth 2017, dywedais wrth Aelodau'r Cynulliad fod ymarfer caffael cystadleuol wedi’i gynnal a bod tîm o Ysgol Fusnes Prifysgol Bangor wedi’i benodi i wneud gwaith craffu a sicrwydd ar ragolygon Llywodraeth Cymru ar gyfer refeniw trethi datganoledig, cyn eu cynnwys yng Nghyllideb 2018-19. Mae'r tîm o'r Ysgol Fusnes wedi bod yn gweithio gyda swyddogion Trysorlys Cymru i ddatblygu a mireinio'r fethodoleg a ddefnyddir i lunio rhagolygon refeniw trethi Llywodraeth Cymru ar gyfer y gyllideb ddrafft.
In my Written Statement on 9 March 2017 I informed Assembly Members that, following a competitive procurement exercise, a team from the Business School at Bangor University was appointed to scrutinise and assure the Welsh Government’s devolved tax revenue forecasts for inclusion in the 2018-19 Budget.  The team from the Business School has been working with Welsh Treasury officials to develop and refine the methodology used to produce the Welsh Government’s tax revenue forecasts for the draft budget.