The first way is that, if they are substantially adapted for a wheelchair user and purchased for their domestic use, they are exempt from VAT. This means there is no VAT to pay when they are bought, either new or second hand. With wheelchair vehicles there is no doubt that they are substantially adapted. When it is a normal vehicle with a small adaptation like a steering ball it can be a grey area.
The exemption applies to a wheelchair adapted vehicle purchased every 3 years. It also applies if your current wheelchair vehicle has been written off in an accident or if your needs have changed and your current vehicle is no longer suitable. You simply sign a form when you purchase the vehicle and the retailer does not charge you VAT. You should then be able to get your vehicle maintained and repaired without VAT being charged. You may have to take the original invoice for the vehicle with you to prove the car was zero rated on purchase.
The second way that disabled vehicles are exempt from tax is if the person using them is entitled to free road tax. This exemption can be applied to any vehicle. If you receive DLA higher rate for getting about or enhanced PIP for getting about you are entitled to this exemption for one vehicle. Tis can be done at the post office with the log book of the car and your exemption certificate(usually sent out by the DVLA with your benefit statement) . If you buy a new vehicle that is allready taxed disabled it can be done on line or by phone with your date of birth and National insurance number.