To propose a method that makes signaling of cost information in a communication network before and during connection.

This method includes a step where a data terminal 1 of a subscriber establishes connection to an exchange 2, the exchange has a call processing function 6 that generates a tariff inquiry 10 to a tariff sever 4, the tariff server replies the tariff acknowledgement 11 for connection on request to a call processing function of the exchange, the call processing function in the exchange transfers the tariff acknowledgement to a CDR generating function 7, the CDR generating function 7 transfers cost information to a cost communication function 8 of the exchange and the cost communication function communicates the cost information to the data terminal of the subscriber.