If your employee e.g. changes their contract from full-time to part-time, here are the recommended steps:
1. Archive the employee* (Configuration→Employees choose an employee→Archive).
2. Add a new user with the same details (same name, email address, date of hire) but with the new work schedule/contract type.
3. Lastly, adjust the entitlement of that employee so it is compatible with their current entitlement.
*Before you do so, we recommend saving the current entitlement of that employee by downloading the Entitlement Report.