Prepaid and Final Invoice Matched to Po

Summary:

Prepaid and Final Invoice Matched to Po

Content (please ensure you mask any confidential information):

Scenario

1. Create Purchase Order(PO) and set to 2-way matching -$10,000
2. Create Prepayment invoice and matched to PO. - $5,000
3. Approve and pay prepaid invoice - $5,000
4. Create final invoice and matched to PO -$10,000
5. DO NOT APPLY Prepaid Invoice to Final Invoice
6. Approve Final Invoice
7. Pay Final Invoice

Why/How was the final invoice paid and not placed on Hold since the prepaid invoice was matched to the PO and not applied to the final invoice?

This resulted in an overpayment.

What are the system checks available to prevent over payment in this scenario?