The identification of employees needing a Temporary TRS ID is done by the BPP Operations staff.
A job (MONTRS32) is run after each payroll throughout the month. Operations will then send you an email notification letting you know that the Temp BPP SSN needs either a Permanent SSN or Temp TRS ID.
If you believe you will be attaining a Permanent SSN before the end of the month, attaining a Temp TRS ID from TRS is not necessary.
Once a Temp TRS ID is obtained, it should be updated in WorkDay.