If an employee has time in lieu when he is resigning, do we need to pay it out like annual leave?
The answer will depend on the source of the entitlement. For example, the General Retail Industry Award permits time off in lieu (TOIL) and states untaken TOIL must be paid out on termination.
However, it might be that the entitlement arises out of a workplace policy which states untaken TOIL is not paid out on termination. Generally, the source will state whether it is to be paid out when employment is terminated.