The present document specifies the Stage 3 of the real-time transfer of Tariff Information between a Charge Determination Point (CDP) and a Charge Generation Point (CGP) by means of the Session Initiation Protocol (SIP). It identifies the protocol procedures and switching functions needed to support the transfer of tariff information related to IP multimedia services. The information needed to support the ISDN User part (ISUP) signalling aspects of charging (ES 201 296 [6]) for Advice of Charge information purposes is also specified, however, it can be used for other purposes as well where applicable. The present document is applicable to an environment where different operators are working together. It is also applicable to a single network operator environment. Whether the present document is applicable to a national environment and/or can be used for inter-network purposes depends on regulatory demands and/or bilateral agreements. It should be noted that there are network requirements and signalling limitations that are not covered because they are outside the scope of the present document. Examples of these are as follows:

• the on-line provided advice of charge information may not accurately reflect the correct charging rate due to discount rates, special charging arrangements, etc. It is out of scope to ensure alignment of this information;
• complaint handling between network operators in case of incorrect advice of charge information;
• explicit encryption or special security mechanisms;
• usage of the transferred tariff information for charging purposes;
• interaction between UE and CGP for possible confirmation of provided tariffs;
• any function behind the CGP towards the UE.

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.

• References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.

The following referenced documents are indispensable for the application of the present document. For dated references, only the edition cited applies. For non-specific references, the latest edition of the referenced document (including any amendments) applies.