A transaction execution system having a multiple account data base and a plurality of transaction terminals in communication with the host. The terminals each include a keyboard, a display, document handlng subsystems, a hardware control subsystem, a communication subsystem and a programmable control subsystem supervising the other subsystems. A user initiates a transaction request by inserting a card, which may have been issued by any of a plurality of cooperating card issuers or banks, into one of the terminals. The issuer identification number is read from the card, and used to search a table of card format and encryption key data. If the corresponding format and key data is located in the table, the terminal requests entry of a preassigned personal ID number through the keyboard. Verification data located on the card by format data from the table is encrypted in response to the key data from the table for comparison with the keyboard entered ID number. If the corresponding format and key data is not located in the table, the card data is sent to the host, which accesses a master table with the issuer identification number, and communicates back to the terminal the corresponding format and key data located in the master table. Once the terminal has checked for correspondence between encrypted verification data and the ID number, in response to format and key data from its own table or communicated from the host, additional transaction data is obtained via the keyboard. Upon command from the host, the host supplied format and key data is purged by the terminal at completion of the transaction, or else retained for future reference.