Car tax in the UK is based on carbon emissions. The table's here: https://www.gov.uk/vehicle-tax-rate-tables/rates-for-cars-registered-on-or-after-1-march-2001

Car tax in the UK is based on carbon emissions. The table's here: https://www.gov.uk/vehicle-tax-rate-tables/rates-for-cars-registered-on-or-after-1-march-2001 https://www.gov.uk/vehicle-tax-rate-tables/rates-for-cars-re... It used to be based on engine size; for years I would get cars with as small engines as possible, simply because it would drop my tax by about 1/3. As for car sizes... it does seem to be having an effect here. A lot of people I know go for small cars, preferring the little five-door hatchbacks. My last one was a Honda Jazz, with a 1.2 litre engine and an absurd amount of space inside; under the new tax system it'd be classed in category D (£110 a year), but I'd be totally unsurprised if the next model made it into category C (£30 a year). My father has a diesel Nissan Note, about the same size, and that is in category C. He's very smug.