After a Candidate has submitted their application, but before it is processed, there will be the opportunity to allow a resubmit if it is felt that there is a need to do so.
If the Parent has already paid, when he or she reaches the payment screen, it will not prompt for a second payment. It will display a message letting the Parent know that the payment has already been submitted.
You can allow a resubmit by going to onBoard:
Select People Finder
Search for the Student
Scroll down to the Application section and click Allow Resubmit