Purchase Order Number
A purchase order number is the buyer's reference for an approved purchase.
A purchase order (PO) number is a unique reference the buyer assigns when authorising a purchase. The supplier quotes it on the invoice so the buyer's accounts payable team can match the bill to the approved order. Many organisations will not pay invoices that lack a valid PO number.
Example
Invoice INV-2041 quotes PO-88713, letting the buyer's finance team match it to the approved order.
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Frequently asked questions
What if the buyer never gave me a PO number?
Ask for one before invoicing — or confirm they do not use purchase orders. Invoicing a PO-driven organisation without the number usually means rejection or long delays.
Should the PO number be on every invoice?
If the buyer uses purchase orders, yes — on every invoice, quoted exactly as issued. Even small typos can break the automated matching in their system.
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