There maybe times that you will encounter errors when processing pay event. Here is one example. See also screenshot 2 that describes the specific error.
Screenshot 1.

Screenshot 2.

That system identifies that the pay event has already been submitted to the ATO. You will need to check on the ATO Portal and confirm if the pay event is already submitted. Once confirmed, use the below steps to manually mark the pay event as complete.
1) Open the Pay Event record and click on the EBMS REQUEST link
2) Edit the EBMS Request record, under the Response Info heading change the Status field to 'Rescheduled Pull' and Save
3) Go back to the Pay Event record and there should now be a 'Mark as Complete' button
4) Click the 'Mark as Complete' button and confirm in the popup
5) The Pay Event should now be green and complete
1) Open the Pay Event record and click on the EBMS REQUEST link
2) Edit the EBMS Request record, under the Response Info heading change the Status field to 'Rescheduled Pull' and Save
3) Go back to the Pay Event record and there should now be a 'Mark as Complete' button
4) Click the 'Mark as Complete' button and confirm in the popup
5) The Pay Event should now be green and complete