English: Yes, so that's set out in legislation and in guidance; we use the same kind of thing for council tax as well. So, obviously, Welsh Government officials and HMRC officials are in constant contact, both in terms of Welsh Treasury and the local government finance officials as well. So, I think that we have a shared understanding as to what a primary home would be. And we see that in effect, if you like, when we look at income tax and the C code. And we had lots of debate when we were introducing the Welsh rates of income tax about how HMRC could ensure that Welsh rates of income tax payers did have that C code attached to their rates of income tax, and we've had very good work done to make sure that we are making sure that as many taxpayers as possible have that code attached to their work. So, we also publish - I think it's annually - a report on the work of HMRC in Wales in relation to those codes as well, and I'd be happy to share more information with colleagues on that, if needed in future. Turning to the longer term, in any change we will obviously be guided by our tax principles. They commit us to designing clear and stable taxes that deliver our progressive agenda, whereby those who are most able to pay pay more than those who are less able. So, whilst powers to vary income tax thresholds would provide additional policy tools for the Welsh Government, we do need to consider carefully our specific needs and the risks, including the risk of a much greater exposure to relative tax base growth between Wales and elsewhere in the UK, and that would be a particular concern to us in relation to the higher and additional rates, where the Welsh Government is only exposed to 10p in each band.
Welsh: Mae hynny wedi'i nodi mewn deddfwriaeth ac mewn canllawiau; rydym yn defnyddio'r un math o beth ar gyfer y dreth gyngor hefyd. Felly, yn amlwg, mae swyddogion Llywodraeth Cymru a swyddogion Cyllid a Thollau Ei Fawrhydi mewn cysylltiad cyson, gyda Thrysorlys Cymru a swyddogion cyllid llywodraeth leol hefyd. Felly, rwy'n credu bod gennym ddealltwriaeth gyffredin o beth fyddai prif gartref. Ac rydym yn gweld hynny ar waith, os mynnwch, pan fyddwn yn edrych ar dreth incwm a chod C. Ac fe gawsom lawer o drafod pan oeddem yn cyflwyno cyfraddau treth incwm Cymru ynglŷn â sut y gallai CThEF sicrhau bod cod C ynghlwm wrth gyfraddau treth incwm talwyr y dreth incwm yng Nghymru, ac rydym wedi cael gwaith da iawn wedi'i wneud i sicrhau ein bod yn gwneud yn siŵr fod gan gymaint o drethdalwyr â phosibl y cod hwnnw ynghlwm wrth eu gwaith. Felly, rydym hefyd yn cyhoeddi - rwy'n meddwl ei fod yn flynyddol - adroddiad ar waith CThEF yng Nghymru mewn perthynas â'r codau hynny hefyd, a byddwn yn hapus i rannu mwy o wybodaeth gyda chyd-Aelodau am hynny, os oes angen yn y dyfodol. Os caf droi at y tymor hwy, mewn unrhyw newid byddwn yn amlwg yn cael ein harwain gan ein hegwyddorion treth. Maent yn ein hymrwymo i lunio trethi clir a sefydlog sy'n darparu ein hagenda flaengar, lle mae'r rhai sydd fwyaf abl i dalu yn talu mwy na'r rhai sy'n llai abl. Felly, er y byddai pwerau i amrywio trothwyon treth incwm yn darparu arfau polisi ychwanegol i Lywodraeth Cymru, mae angen inni ystyried yn ofalus ein hanghenion penodol a'r risgiau, gan gynnwys y risg o fod yn llawer mwy agored i dwf cymharol y sylfaen dreth rhwng Cymru a mannau eraill yn y DU, a byddai hynny'n bryder penodol i ni mewn perthynas â'r cyfraddau uwch ac ychwanegol, lle mae Llywodraeth Cymru ond yn agored i 10c ym mhob band.