We need to disable 'Make Amendments' from timesheet. Once employee submit timesheet they must not have access to amend it only admins can Make Amendments.
Reproducing the Issue
Login as end-user and go to timesheet for current week submit timesheet. After the timesheet is approved you can see Make Amendment Button on the right hand side corner.
The Time Recording Admissibility assigned to the employee's job information has setting called "Amendments Allowed" = Yes.
You need to change the setting "Amendments Allowed" to No, in case you wish to hide Make Amendments button from the employees.
Note: This setting is not respected for managers / admins.
In the case of authorized managers or administrators on behalf of employee, make amendments to an approved time sheets can be done regardless of the editing "Amendments Allowed" settings and earliest possible time entry date defined for the employee.
Make Amendments Time Recording Admissibility Timesheet SuccessFactors Employee Central , KBA , time recording admissibility , timesheet , make amendments , LOD-SF-EC-TIM , Time-Off , How To