Customers can obtain VAT relief on an adapted vehicle for a disabled user if the following criteria are met: the owner or user of the vehicle is normally a wheelchair user, it is only being purchased for personal and domestic use, the vehicle has been permantently and susbstantially adapted to meet their requirements and you have not obtained VAT relief on a vehicle in the past three years. You can find the HMRC form here - www.gov.uk/government/publications/customer-declar...a - which should be completed and handed to the dealer. If they are refusing to comply, you can write a letter of complaint to the dealer principal or trade body if the dealer is a member of one.