A system for determining and accounting for the costs of transactions. The system is particularly suited for determining and accounting the costs of shipping goods. The system includes an input device which is located at the shipper's (or other buyer's) premises and a central data processing facility. The input device receives information defining a shipment sufficiently so that the cost of that shipment may be determined in accordance with the rates of a carrier (or other seller), and uploads the information to the central data processing facility. Preferably, the input device includes rate information and software for determining shipment costs locally. The central data processing facility maintains accounts for a shippers and carriers, appropriately debits and credits costs for each shipment and periodically issues statements of their accounts to all shippers and carriers. In a preferred embodiment, shippers may maintain a payment account with a trustee bank and the system may from time to time issue instruction to the trustee bank to make appropriate payments to each carrier. In another embodiment, carriers may from time to time enter new rate information into the system.