How does a purchase order work? A purchase order (PO) is used to place an order; a PO is not a form of payment. An order is placed, after which a PO is dispatched. Then, the invoice is issued and payment of the invoice is issued through the Controller’s Office. Updated on June 24, 2021 Tagged: InvoicepaymentPOPurchase Ordertraining Was this article helpful? Yes No Cant’t find what you are looking for?Sends us a messageContact the KB Team