How to prevent requester approval of non-PO invoices until distributions are entered by requester

Summary:

The issue is that the requester is able to approve the invoice even if no distributions (account coding) have been entered. This causes problems because invoices get approved without proper coding, and AP has to correct them later.

Our requirement:

• The requester should still receive the approval notification (so the process does not change for them).
• But before the requester can actually approve, the system should require that distributions are entered.
• In other words, the requester should not be able to approve if the invoice has no distributions.

Goal:
We want to make sure all non-PO invoices submitted through the Supplier Portal must have valid distributions