For successful on-time payment, an invoice needs to include an invoice number along with the pertinent billing information. The matching of an invoice number, vendor ID, and dollar amount works to eliminate duplicate payments. If the invoice you receive does not have an invoice number, ask the vendor to reissue a corrected, complete invoice. All invoices needing payment against an established Purchase Order should be sent by the vendor directly to Accounts Payable as instructed on the purchase order received by our vendors.