Abstract: A method for implementing bills association mainly includes generating a session identifier corresponding to a call; indicating bills with the session identifier by communication devices which are required to generate the bills corresponding to the call, to implement the association between the bills generated by the communication devices. Embodiments of the present invention further provide a system and a CO switch for implementing bills association. The method and the system of the present invention may implement the association of bills in one call. The association includes the association between ordinary bills and the association between ordinary bills and intelligent bills. In this way, telecom operators may charge a call by collecting the bill generated by each CO switch according to the Call ID to improve the precision and the efficiency of the accounting process.