Ace Payroll uses the ID of each employee to index the employee with all the associated data files used by the program.
When you delete an employee, they are deleted from the employee file and a few associated index files. The records of wages paid to the employee are not deleted from the system otherwise you would lose the integrity of your financial records.
If you have deleted your employee by mistake, or have some other reason to add back a previous employee, simply add a new employee with the exact same ID as the one deleted.
Records of all wages paid to the employee can then be retrieved as before. Simply add back their personel data such as names, IRD number etc and you are back where you started.
The downside of this approach is that you cannot load a new employee with the same ID as a previously deleted employee.