A method and system for content-based billing in IP-networks, carry out and transmit to a control gateway module the authentication and/or service authorization of an IP-node based on the IMSI of the SIM card of the node for HLR and/or VLR of a GSM network and guide the access of the IP node to the content of a network content provider through said control gateway module, control involved costs by means of the nodule on the base of the access target address, detect call detail records according to the IP-node services by a core engine module, detect at least the identity of the IP-node and/or the time and/or a provider of the required services by means of the call detail records during access to the control gateway module, transmit the data to the billing module and compute call detail records and/or clearing data based thereon and/or TAP files through the billing system of a service provider or a financial institution. The disclosure relates, in particular to the mobile IP nodes in heterogeneous networks.