On occasion dealers will have new vehicles in stock which are not registered immediately, so there can be a gap between the build date and the date of first registration, but three years is an unusually large gap. Although the car is three years older than you first thought it is still new in the sense that it has clearly not been used given the mileage. If you are unhappy with the situation you could go back to the dealer - if they advertised it as a 2024 car you could potentially argue that it has been mis-sold, although they may well argue that it was advertised on the basis of the registration date. If you can evidence that it was advertised as a 2024 you could attempt to reject it, you can read more about this process here - www.honestjohn.co.uk/faq/consumer-rights/ although you may have more success in asking for a small refund as compensation.