"The present document has been prepared to provide a model for designing and operating the checking-up on metering and billing processes of Service Providers. Because the checking-up approach of the present document is end-to-end (i.e. using a ""black box"" approach from the actual electronic communications generation to the checking-up on their billing)@ it is intended that these requirements are applicable to the metering and billing of any kind of services offered by the Service Providers. The goal of the present document is to define a standardized checking process that could be implemented by any stakeholder and is auditable by a third-party@ leading to trustworthy performance indicators about the integrity of billing issued by a Service Provider. NOTE: It is important to note that the present document does not provide any model for designing and operating the metering and billing process itself."