Accounts payable is the riskiest ever account that accounting staffs can be fallen in. When it is overpaid company will loss money. When it is underpaid company loss credibility and jeopardizes business relationships. Inaccurate numbers, wrong vendors, less chance to perform payable analysis are also as bad.
The more complex a process, the more chance to get inaccurateness, so the more documents to be collected and get matched each other, the longer the route will be passed to get approval, and it also means that the more time required to complete the task.
How if you just forget all those documents and stick on a single document—the receiving slip?
At least in my experience, there is no chance for the accounting staff to do a mistake just by paying the payable based on the receiving slip that got approval already. No matter what the PO is, as long as you pay only the goods or services received, everything is going to be okay.
It means other custodians in other sections should have been done with check and match, and there is no need at all for the accounts payable staff to repeat the tasks. That is the real point. And this is the chief accountant or controller’s task to make sure that other custodians have been done with matching and checking before any invoices get paid.