Employee: repayment of bonus

My client has been a successful director over the years of some medium-sized retailing companies. He has now been offered a position with a company, whereby 50% of the package would be salary, and the balance would be a large bonus every year, which would be repayable in certain circumstances. Am I right in saying that there will be no tax relief if and when part or all of a bonus has to be repaid? Is there a way in which a bonus can be paid conditionally, but with no PAYE until the bonus ceases to be repayable?