(1)A deduction is to be made from the provisional sum calculated under step 3 of section 157 if, as a condition of the van being available for the employee’s private use, the employee—
(a)is required in the tax year in question to pay (whether by way of deduction from earnings or otherwise) an amount of money for that use, and
(b)makes such payment.
(2)If the amount paid by the employee in respect of that year is equal to or exceeds the provisional sum, the provisional sum is reduced so that the value of exclusive availability is nil.
(3)In any other case the amount paid by the employee in respect of the year is deducted from the provisional sum in order to give the value of exclusive availability.
(4)If the van is a shared van for any part of the tax year in question, the reference in subsection (1) to the employee’s private use in that year is to be read as a reference to the employee’s private use in that part of the year when the van is not a shared van.
(5)In this section any reference to the van being available for the employee’s private use includes a reference to the van being available for the private use of a member of the employee’s family or household.