To block an employee from entering the company, use the [Deactivate] feature.
  PC: [Web Manager Mode] > [Employees] > Select the employee > click [Deactivate]
 Mobile App: Tap [Menu bar] > [Employees] > Select the employee > Tap [Edit] > Tap [Deactivate] 
 *Deactivating an employee does not delete their records. To delete all work schedules and attendance records, follow these steps:
 PC : [Web Manager Mode] > [Employees] > Set the [Show Inactive Employees] toggle on > Select the employee > Click [Delete Employee Permanently]
 Mobile App : Tap [Menu bar] > [Employees] > Go to [Inactive] tab > Select the employee > Tap [Delete Employee Permanently] 
 For more information, please refer to 
Deactivate Employees.