This specification defines the APIs that an Operator Platform would use for the realisation of its Southbound Interface to the Charging Function. This would enable the Operator Platform to trigger the charging for the different services that it exposes and the various charging scenarios that an operator may choose for charging those. The APIs would also allow to provide the charging function with part of the API payload that would be relevant for the Charging. The APIs covered for this interface are exposed by 3GPP’s Charging Function. This specification defines a baseline for the APIs that that function is expected to support to enable the Operator Platform use cases. This initial version of the specification is aligned with the requirements in GSMA PRD OPG.02 v5.0.