When an employee is no longer working in your organization you can choose to Disconnect that Employee. Go to Administration > user and the employee tab and click on the three dots and 'edit'. Select Disconnected under the option Status.
Active - Employees can see the organization, and their projects and will be matched at the upcoming projects and roles.
Disconnected - The employee no longer has access to the company.
Preactive - The employee is connected to your company and can see the Overview, create Resumes and update their profile, but can not see any Company Information. The Employee can be assigned to Roles. The upcoming employee will be marked as Joining soon for all within the organization.