The method and system manages supply chain purchases of goods and services (G-S) using a distributed computer system coordinating interested customers with vendors who offer G-S. The system uses a database or accesses a vendor's database having default offer records which include G-S descriptions, price, payment terms, delivery data, and set-aside parameters. A sophisticated system includes customer specific offer records for approved customers with specific price, payment, delivery and set-aside parameters. Customers search the database, and if previously registered and accepted by the vendor, the customer can reserve a defined quantity of G-S in accordance with set-aside parameters, request a quote, and/or purchase G-S from the vendor. Further, the system rates the vendor and the customer based upon timely performance of, for the customer reservation followed by purchase of G-S within the defined quantity, and for the vendor, timely delivery of G-S and timely notice of customer acceptance.