Without the HR module
Find the employee and click on ‘Edit’
TIP: To delete employees entered in error, enter the start date the same as the end date.
Level 5 users can reverse decisions to make people a leaver simply look for the employee under deleted employees then under the employment tab you will see the option to bring them back if a mistake was made or you need to add in extra hours and then make them a leaver again.
See Making General Changes to Employees if you are unsure how to get to the employee profile.