Hi crowe001,
For a taxable benefit amount to be paid by an employee it would need to be reported on P11d, you would also need to establish if OPRA applies.
Information on this can be found here:
Optional remuneration arrangements (480: Appendix 12)
This will advise which figure to use when calculating the taxable amount.
The benefit of salary sacrificing for a benefit is that the contract is in the companies name meaning it is only subject to class 1A national insurance so the employee will not pay any National Insurance on it.