Prepayment Exceeding Purchase Order Amount

Organization Name (Required - If you are an Oracle Partner, please provide the organization you are logging the idea on behalf of):

LOLC Technologies Ltd.

Description (Required):

The user is attempting to issue a prepayment against a purchase order and is able to create a prepayment that exceeds the PO amount.

Are there any controls or workarounds to restrict this?

Use Case and Business Need (Required):

Enhancement Request / Service Request:

Enhancement Request