Payment is the money rendered by the Postal Service to the supplier in exchange for the products or services provided upon receipt of a proper invoice. The CO, in conjunction with Finance, must ensure that all payments are made once a legitimate invoice has been processed during the Process Invoices topic of the Make Payment task of USPS Supplying Practices Process Step 5: Measure and Manage Supply. Failure to make payment, or late payment, can have harmful effects, such as damaged working relationships, time delays, and interest accrual.