Purchasing

Planned

Requisition to purchase order to goods receipt to supplier invoice, with a three-way match.

Three-way match
Order, receipt and supplier invoice meet, and the discrepancy surfaces before payment rather than after it.
The supplier’s own number is the control
A supplier document is recorded under the number they wrote, unique per supplier per set of books. That uniqueness is what stops an invoice being paid twice.
Requests route like everything else
A purchase request goes through the same approval machinery as every other document, not a special one of its own.

Three-way match