The CO2 value for cars registered from 2008 onwards is captured by the Revenue Commissioners from the Certificate of Conformity provided by the manufacturer and transmitted to the National Vehicle and Driver File. The CO2 emissions for new vehicles are calculated in accordance with specific standards for this purpose, and I am not aware that the tests can be applied in a comparable way to pre-2008 vehicles. Allowing a CO2 rating to be taken at a point in time other than manufacture would potentially lead to owners of vehicles (both pre- and post-2008) providing different CO2 readings over the lifetime of the vehicle, leading to significantly increased difficulty in administering the motor tax system. Any loss in revenue arising would have to be compensated for elsewhere in the motor tax system or through the taxation system generally. I have no plans to change the basis for charging motor tax for vehicles registered prior to 2008 from engine capacity to CO2 emissions.