Here's an update for all cars first registered from 1 April 2017
For all new cars registered on or after 1 April 2017: The rate for the first year is still based on CO2 emissions. From the second year onwards, the standard rate kicks in – £140 for petrol and diesel cars, or £130 for hybrids and alternative-fuel cars.
If your car cost more than £40,000, you have to pay an extra £310 a year, for five years. This is on top of the standard rate (years two to six).
Low-emission cars that produce less than 100g/km of CO2 are no longer exempt from paying car tax. Only zero-emission cars are exempt from car tax, but are still subject to the £40,000 rule.
Additional rates and rule for cars first registered from 1 April 2018
From 1 April 2018, rates in the first year are slightly higher for all cars. As with the 2017 rules, the first year ownership is still based on CO2 emissions, and will then go to the standard rate. Plus anybody who buys a new diesel car that doesn’t comply with RDE Step 2 (RDE2) emission testing will pay a higher amount of car tax again in the first year of ownership.
Only diesel cars are affected. Diesel vans are exempt. New RDE tests Step 1 (RDE1) came into force in September 2017, but all new cars do not have to comply with these new testing procedures and limits until 1 September 2019. RDE Step 2 does not come into force until 2020-21.
The maximum additional amount diesel cars owners will have to pay in the first year is £520. That’s for cars that emit 191 to 225 g/km of CO2. Read more here