EIM36750 | Deductions from earnings: capital allowances: particular items of plant or machinery: cycles and motor vehicles: general

Section 36 CAA 2001

An employee cannot claim capital allowances for a cycle or a 'mechanically propelled road vehicle' such as a car, motorcycle or van.

The only way an employee can get tax relief for using their own vehicle for work is by a deduction for mileage allowance relief (see EIM31330 onwards).