There is a MicrOpay IQ Report available that can assist you.
Go to Common, IQ.
Find IQB-STP - STP Audit Report.
For Include Terminated, enter either 0 (False) to exclude Terminated employees or 1 (True) to include them.
Select OK.
The results will list employees with any validation messages. Review the Message column for details and, if necessary, fix them processing the STP Event.
If the employee doesn't appear on the report:
Go to Payroll, Maintenance, Employee, Employees.
Edit the employee who doesn't appear.
Select Termination Details and check to see if Exclude from STP Reporting has been ticked.