In transactions involving deliveries of packed goods, the Evaluated Receipt Settlement (ERS) system is usually employed.  The packing slip included in the goods delivered serves as the invoice in these transactions.  The seller and the buyer use the data in the packing slip to record the delivery and the obligation of the buyer to pay the seller. 

The shipper of goods or the supplier bases their shipment on an Advance Shipping Notice while the purchaser confirms the purchase contract, checks the received shipment as to identity and quantity and sends payment as per invoice received.