It makes a big difference whether a double cab pick up is treated as Car or a Van for tax purposes, in summary:

1. Benefit in Kind on Cars is linked to CO2 where as on a Van its Flat Rate (and could be zero if your private use is insignificant)
2. Vans qualify for the Annual Investment Allowance, Cars have restricted Capital Allowances
3. You can reclaim VAT on Vans but its much harder to reclaim VAT on cars

HMRC have some guidance in EIM23150….

Under this measure, a double cab pick-up that has a payload of 1 tonne (1,000kg) or more is accepted as a van for benefits purposes. Payload means gross vehicle weight (or design weight) less unoccupied kerb weight (care is needed when looking at manufacturers’ brochures as they sometimes define payload differently).

Under a separate agreement between Customs and the Society of Motor Manufacturers and Traders (SMMT), a hard top consisting of metal, fibre glass or similar material, with or without windows, is accorded a generic weight of 45kg. Therefore the addition of a hard top to a double cab pick-up with an ex-works payload of 1,010 kg will convert the vehicle into a car (net payload reduced to 965 kg). Under this agreement, the weight of all other optional accessories is disregarded. HMRC has also adopted this treatment.

http://www.hmrc.gov.uk/manuals/eimanual/eim23150.htm

A double cab with a payload in excess of 1000kg can still be classified as a car if the taxman dealing with the case decides it is a car. You may have to justify a genuine business need for the vehicle.

steve@bicknells.net