An electronic commerce system includes a client computer and a server computer interconnected by a public packet switched communications network. The client computer is programmed to transmit to the server computer an order acceptance request that includes a plurality of terms or conditions of a proposed offer for a purchase, including multiple options of at least one of the terms or conditions of the offer. The server computer is programmed to process the order acceptance request based on pre-programmed criteria and, based on the processing of the order acceptance request, to transmit to the client computer an order acceptance response that includes a plurality of amendments to the proposed offer for the purchase, including selection of an option of the at least one of the terms or conditions.