Abstract: A method for authenticating a transaction is disclosed. The method comprises the steps of: receiving data identifying a region where a transaction is being requested; receiving data identifying a mobile communication device associated with a person requesting the transaction; determining from Location Register (LR) data for the mobile communication device data identifying a region where the mobile communication device is located; comparing the data identifying the region where the transaction is being requested with the data identifying the region where the mobile communication device is located; and authenticating the transaction in dependence on the result of the comparison.