You can find out the rates using the DVLA service if you have the id from the V5C.

www.gov.uk/check-vehicle-tax

You can put the specific car into vehicleenquiry.service.gov.uk/ but you'll need the 11 digit reference number from the V5C to get the tax rate.

Im am thinking of buying a second hand Diesel SUV but want to negate having to pay the ‘Premium Car Tax’ for any vehicle registered after 1/4/17 which currently stands at £335 per year for years 2-6 on top of that vehicles tax rate. Rather than relying on a dealer to tell me if the ‘list price’ (inc. options etc.) was under £40,000, is there a reliable database to consult to determine this? Call me suspicious but Im not 100% confident in a sales person to furnish me with the definitive answer as they have a vested interest in selling a specific car. I have scoured the interweb for the answer without much success.

People who historically have bought older premium cars now need to bear this in mind, as their possibly cheap but luxurious/fast barge may not be teh bargain they once might have been, especailly with prices generally rising in the last few years, particularly now.

May I presume that EVs are exempt from this additional tax? If not, then it rather devalues the 'green' argument for it in the first place.