It's just a tax on new vehicles, added to the selling price.
After the first year the rates are as usual.
Worth bearing in mind if buying nearly new secondhand, it, together with the 20% VAT, is something for the first owner to suck up, not to be passed on in the S/H price compared with new, IMO.
Fleets and dealers have ways around this, writing off against tax or losses, hence the sometimes attractiveness of pre-registered, ex demo, ex fleet etc. stuff. Sometimes never left the showroom or just run around by one of the staff as a company vehicle for a few months to put some miles on the clock.
Same as VAT on expensive things, deduct 20% from the new price before deciding what would then be a fair price.
Same with warranty. Some sellers don't understand, asking say something like 80% of list (not real) price for something they claim to have only used a few times. Trying to explain that the street price is X, take off the 20% VAT that you paid, deduct for out-of warranty, even...