Various mechanisms are disclosed for a service domain charging system that can interact with underlying networks. A service domain charging architecture is defined with several logical functions. Service-based charging types may be and applied to existing event, session, online, and offline charging mechanisms. Service domain charging messages may be exchanged over the X, Y, Z reference points. An E reference point may be used for interfacing with a service domain billing system, and a B reference point may be used between a service domain billing system and underlying network's billing system.