Answer
Three-way matching compares three documents before an invoice is paid: the purchase order (what was ordered), the goods receipt note (what was received), and the supplier invoice (what is billed). If quantity and price agree across all three within tolerance, the invoice is approved; discrepancies raise an exception.
PO: 100 units @ $25 = 2,500
GRN: 100 units received
Invoice: 100 units @ $25 = 2,500 -> match, approve for paymentReal-world example An invoice passes three-way match automatically because the PO, receipt, and invoice all show 100 units at $25.