A transaction processing system for the real time authorization of payment transactions. The system comprises a verification system (4) connected to an issuer card management system (3). A cardholder can access the system via an interface (2) which can be for example the Internet, a wireless device, telephone, or a branch visit. The interface allows the cardholder to input rules governing how their credit card transactions are to be authorized. When the cardholder initiates a purchase transaction with their credit card, an authorization request is passed from the card network to the verification system which executes the rules created by the cardholder in order to approve or deny the transaction.