Abstract: A method of performing a transaction over the Internet between a customer (1) and a vendor (2) using a payment card issued by a card company is disclosed, comprising the steps of: prior to any transaction using the method, assigning and advising a customer of an identifier corresponding to a payment card number of the customer's payment card and storing the identifier with the card number and a telephone number of the customer (1): and at the time the transaction occurs, receiving the identifier from the customer (1) over the internet, establishing the card number from the identifier, calling the customer using the telephone number to confirm the transaction, obtaining authorization of the confirmed transaction from the card company (5) and communicating the authorization to the vendor (2).