It is not that straightforward. There is bad news and there is good news.
The bad news is they are adding new bands based on CO2 emissions. There are 13 bands named A to M. If you have a gas guzzler (as I have) then you will be interested in the top bands:
Band K = 201 - 225 g/km -> �210 road tax
Band L = 2256 - 255 g/km -> �400 road tax
Band M = over 256 g/km -> �400 road tax
The good news? Well, there was a lot of fuss about re-banding cars registered before March 2006. This was considered unfair because these cars were bought before there was any mention of new bands. The government gave in. If your car was registered before March 2006 (as mine was) then the highest band is K:
Band K = over 201 g/km -> �210 road tax
http://www.direct.gov.uk/en/Motoring/OwningAVe hicle/HowToTaxYourVehicle/DG_172916