How to disable 'Create Invoice without a PO' only from supplier portal

Summary:

Our business requirement is to allow the supplier to enter a PO match invoice from the supplier portal. They should not be give an option to generate invoices that does not match a PO.

Content (please ensure you mask any confidential information):

The “Self Service Payables Invoice Entry” role allows suppliers to create all types of invoices—both matched and unmatched to a PO.However, there is no option to disable or hide the “Create invoice without a PO” feature within the supplier portal UI.

Removing the “Self Service Payables Invoice Entry” role and 'Enter unmatched payables invoice as supplier'; and adding the “Enter Matched Payables Invoice As Supplier” privilege results in suppliers losing match invoice creation capability. Although suppliers can attempt to start an invoice with this privilege, they are unable to complete it due to the missing option to choose a Remit-to site—this is not an acceptable user experience.