The present document covers offline charging for the IMS. For clarity, the terms Offline Charging and Online charging as applied to the IMS are defined here in clause 3. These definitions are the same as listed in [2].

The IMS charging architecture details, requirements, definitions and principles are listed in [2] and therefore are not repeated here.

In the present document the charging data triggers, message content and format are specified along with the transport of these messages using the Diameter protocol. Details about charging message flows and the definitions of the Diameter AVPs are also included in the present document. This information is divided into two main clauses: Online Charging and Offline Charging.