A system and method for performing an on-line ATM/POS transaction utilizing checking or savings account funds over a public access network is disclosed. The invention comprises creating an electronic financial transaction instruction comprising card information and security information that are encrypted for secure transmission over the public access network. The card information identifies a checking or savings account number of a purchaser. The security information identifies a personal identification number associated with the identified account number that authorizes the use of the account number in an on-line ATM/POS transaction. The financial transaction instruction is decrypted by a financial institution and reformatted to form a transaction request suitable for transmission over an on-line ATM/POS transaction system. The transaction request is then processed like a typical ATM or merchant POS on-line ATM/POS transaction. As such, approval and settlement of the financial transaction instruction is obtained in real time. Thus, the present invention provides an on-line ATM/POS transaction capability utilizing checking or savings account funds from a public access network, such as the Internet or electronic mail.