What CO2 emissions (g/km) means for you
For cars registered from 1 March 2001 to 31 March 2017, the CO2 figure set the car tax band, from A (£20) to M (£790). For cars registered from 1 April 2017, it no longer sets car tax, which is a flat £200 standard rate plus a supplement for expensive cars.
Car tax doesn't transfer to a new keeper, so the car must be taxed before you drive it. Electric cars have paid car tax since April 2025. Our free check shows the car's tax status before you buy.