A data processing system issuing electronic certificates through “online” networks. Each electronic certificate includes transaction data and identification data, and can be printed out on a printing device linked to a consumer's personal input device, or electronically stored in a designated data base until a specified expiration date. Consumers access the data processing system online, browse among their choices, and make their selections. Certificate issuers have online access to the data processing system and can create or revise offers, and provide various instructions pertaining to the certificates, including limitations as to the number of certificates to be issued in total and to each individual consumer.