A POS terminal 8 in a transaction system 1 transmits control data instructing executing a transaction-related process during a transaction; a recording device 12 receives the control data, executes a process based on the control data, transmits transaction information based on the control data and transaction identification information identifying the transaction information, and outputs a 2D code representing the transaction identification information; a terminal 14 reads the transaction identification information from the 2D code output by the recording device 12, and transmits the transaction identification information that was read and a customer ID, which is identification information to store; and a control server 10 receives the transaction information and transaction identification information from the recording device 12, receives the transaction identification information and customer ID from the terminal 14, and relationally stores the transaction information and customer ID when both of the received transaction identification information match.