Currently there is no way to block Accounts Payable from having the ability to pay another vendor for an invoice other than the vendor specified on the PO. If a user has rights to make payments they can make a payment for any vendor regardless of who the invoice is for. This alerts any time Accounts Payable pays an invoice to a vendor that is not the vendor on the Purchase Order.
There are no variables for this alert. Alert will fire any time a payment is made using Vendor Number different from Vendor Number on Purchase Order.
How is this error typically made? When creating the vendor invoice, you can select one vendor, add the PO's from that vendor to vendor invoice and then change the vendor to a completely different vendor. Then when processing the invoice for payment, the payment is recorded against the other vendor.
Validated by viewing Payment via Accounts Payable / Payments:
And comparing to Purchase Order via Purchasing / Purchase Orders: