This order placement and payment settlement system provides secure transactions in online shopping by means of the intermediation of settlement bodies that authenticate buyers and sellers, allowing each party to conduct business with confidence in the other. The buyer's computer or other data terminal accesses the seller's server to obtain purchase order information and transmits such information as is required to the server of the settlement body. On the basis of that information, the server of the settlement body references buyer credit databases provided to it and then transmits the purchase order to the seller's server only when the buyer is capable of making payment. The settlement body server also uses a trustworthiness ranking of the seller to determine the timing of settlement and effects settlement unless the buyer objects to settlement before that time. The system thus provides both the buyer and the seller with enhanced confidence in the integrity of the transaction.