(1)This section applies where—
(a)a later accessory is available with the car in the tax year in question,
(b)that accessory (“the new accessory”) replaced another qualifying accessory (“the old accessory”) in that year or an earlier tax year, and
(c)the new accessory is of the same kind as the old accessory.
(2)If the new accessory is not superior to the old accessory, the cash equivalent of the benefit of the car for the tax year is to be calculated under step 2 of section 121(1) as if—
(a)the replacement has not been made, and
(b)the new accessory is a continuation of the old accessory.
(3)If the new accessory is superior to the old accessory and the conditions in subsection (4) are met, the cash equivalent of the benefit of the car for the tax year is to be calculated under step 2 of section 121(1)—
(a)as if the old accessory was not available with the car in that tax year, or
(b)where the price of the old accessory would (apart from this section) be added to the price of the car under step 2 of section 121(1) as an initial extra accessory, as if it was not available with the car at the time when the car was first made available to the employee.
(4)The conditions mentioned in subsection (3) are that—
(a)the old accessory was a non-standard accessory, and
(b)both the old and the new accessory would (apart from this section) be taken into account under step 2 of section 121(1) in calculating the cash equivalent of the benefit of the car for the year.
(5)For the purposes of this section a new accessory is superior to an old accessory if the price of the new accessory exceeds whichever is the greater of—
(a)the price of the old accessory, and
(b)the price of an accessory equivalent to the old accessory at the time immediately before the new accessory is first made available for use with the car.
(6)In this section references to the price of an accessory are to—
(a)its list price, if it has one, or
(b)its notional price, if it has no list price.