Rhoddwyd biliau trethi i'r busnesau dan sylw wedi'u hôl-ddyddio i 1 Ebrill 2005, ac yn 2008 cyflwynodd Llywodraeth y Cynulliad (a Llywodraeth y DU yn Lloegr) ddeddfwriaeth i ganiatáu talu elfen ôl-ddyddiedig y trethi fesul rhandaliadau dros 8 mlynedd.
The affected businesses in Wales were issued with rates bills backdated to 1 April 2005 totalling around £4 million, and in 2008 the Assembly Government (and, in England, the UK government) passed legislation to allow the payment of the back-dated component of the revised rates liability to be made by instalments over 8 years.