Leavetrack allows you to archive users when they stop working for you. This preserves their record for your business.
If an employee rejoins, you can either create a new record for them or reactivate their old record. Reactivation brings them back as if they had not left i.e. all their old records and notes will be there. You will need to ensure that you update any holiday entitlements accordingly.
To reactivate an employee, navigate to Account > Employees and ensure the All Employees filter is active. You will see a link to "Restore User".