A system and method for verifying, authenticating, and providing notification of a transaction, such as a commercial or financial transaction, with and / or to at least one party identified as engaging in the transaction and / or identified as having a potential interest in the transaction or type of transaction, are provided. A central system accepts information regarding a transaction, including information about at least one party identified as engaging in the transaction, such as by a credit account number or Social Security number or merchant account number, and / or identified as having a potential interest in the transaction. Based on the information regarding the transaction and any supplemental information the central system determines, the central system communicates with and / or to at least one party and / or additional or alternative parties, via at least one communications device or system having a communications address, such as a telephone number or Short Message Service address, predetermined as belonging to the at least one party and / or additional or alternative parties. Via said communications, at least one party having an interest or a potential interest in the transaction may be notified of it, and may further be enabled or required to supply additional verifying or authenticating information to the central system. If the transaction was initiated or engaged in via a communications link, such as via the Internet, said communications preferably occur over at least one different communications link and / or protocol, such as via a wireless voice network. The central system may then compute a result based on the outcomes of said communications, and may then transmit the result to the user and / or to a second system or device.