In the world of business transactions and financial management, invoices play a crucial role. They serve as a detailed record of goods or services provided, as well as the agreed-upon terms and conditions of a transaction. To ensure clarity and accuracy, each invoice is assigned a unique identifier known as a PO number. In this article, we will delve into the basics of invoicing, the significance of a PO number, how to locate it on an invoice, and its relationship to effective invoice management.