Currently, there are very limited circumstances when a formal challenge to a Council Tax band can be made as the current valuation list has been in force for a long time, since April 2005.
Ar hyn o bryd, dim ond o dan amgylchiadau cyfyngedig iawn y gellir herio band Treth Gyngor yn ffurfiol am fod y rhestr brisio bresennol wedi bod mewn grym am amser hir, ers mis Ebrill 2005.