Secure electronic transaction system is provided between a plurality of computer systems and other electronic terminals wholly or partly over a public communication system such as the internet, a closed communication system such as a banking network or point-to-point communications such as dial-up connections and leased lines. Secure transmission of transaction information instructions and payment instructions is provided from a customer's computer system to the customer's bank's computer system. The bank's computer system processes and evaluates the instructions and transmits by way of secure transmissions the transaction instructions and payment instructions to the merchant's computer system.
