Abstract: A transaction processing system for enabling users to authorize transactions, comprising: at least a first data communications interface and a second data communications interface; a data receiver arranged to receive transaction data, relating to a transaction to be authorized by a user, via a first data communication path, at said first data communications interface; a communications controller arranged to conduct communications over a second data communication path, different from said first data communication path, with said user at said second data communications interface; a data authentication system arranged to conduct a secure access procedure, via said second path, in which authentication data is received and said authentication data is verified, wherein the communications controller is arranged to receive: a first transaction reference relating to said transaction from said user, said first transaction reference not having been previously transmitted to said user via said second communication pa

Abstract: A method of operating a transaction processing system (19) for confirming orders placed over a public data network (1), comprising: receiving first order references from a number of different merchant sites (7) via first data communication paths; receiving payment data and second order references from a number of customers via second communication paths different from said first communication path; and matching said first and second order references and settling payments.

Abstract: A method of operating a transaction processing system (19) for confirming orders placed over a public data network (1), comprising: receiving first order references from a number of different merchant sites (7) via first data communication paths; receiving payment data and second order references from a number of customers via second communication paths different from said first communication path; and matching said first and second order references and settling payments.