An employee's login access is removed upon entering the termination date in the employee's Employment profile- regardless of whether it is a current or future date. With that said, we would advise you not to terminate an employee with a future date if you still want them to access the site.
When a company is terminated, all user logins will be disabled for both employees and HR users. Broker users will still be able to access the group by unchecking the "Active" box on the home page. This will allow the company to appear in the drop-down menu. For more information, view our article on how to Terminate a Company.