Charging plays a critical role in IMS networks. After all, new services will only be built, equipment and services sold, if they can be billed.

IMS includes both online and offline changing methods and mechanisms to give operators the greatest flexibility for their future billing needs. Online billing enables services to be billed in real-time and can affect the services that are provided. With offline billing, services are not affected by the charging information.

Not only does IMS allow operators to charge differently for different types of media (e.g. voice, text, pictures and video), it also allows them to charge differently for the same type of media in different services.

For example, operators can change more for video content in a Video On-Demand service than for video content in an MMS message. Operators will also be able to charge according to Quality of Service (QoS), charging more for a video stream in a Push-to-Show session than a video stream in a game.

While most billing models today include buckets of minutes or service baskets for flat monthly fees, IMS opens the door to usage-based billing and other competitive billing plans.