Mae achos cryf dros ddatganoli treth ar dir gwag, o gofio ei fod yn cyd-fynd â phwerau datganoledig sy'n bodoli eisoes a'i gwmpas cymharol gul. Neilltuwyd dwy flynedd o waith i sicrhau bod gan Lywodraeth y DU'r wybodaeth yr oedd arni ei hangen i ystyried yr achos hwn. Cytunwyd mai mater i Lywodraeth Cymru oedd gwneud unrhyw benderfyniadau polisi ynghylch sut y byddai unrhyw dreth ddatganoledig newydd yn gweithio, ac mai mater i'r Senedd fyddai penderfynu a ddylid pasio unrhyw dreth mewn cyfraith.
There is a compelling case for the devolution of vacant land tax, given its alignment with existing devolved powers and relatively narrow scope. Two years of work went into ensuring the UK Government had the information it needed to consider this case. We agreed it was for the Welsh Government to make policy decisions about how any new devolved tax would operate, and for the Senedd to decide whether to pass any new tax into law.