"Making good" simply means giving something in return for the benefit. What is being made good is the expense incurred by the employer or other person providing the benefit. It follows that in order to make good that expense the employee will give money, or something that can be measured in money. Usually the employee will "make good":
Any of these methods is acceptable.
The giving of services by the employee, or anything that is
not measured in money terms is not "making good", see Stones v Hall
(60TC737).
(This text has been withheld because of exemptions in the
Freedom of Information Act 2000)
As regards "making good" by waiver of remuneration see
EIM21122.