the renewed approach to bill- ing has led to different types and models. Some of the key terminologies used in billing that the reader has to be familiar with are: 1. Account: Each customer is handled as an account in the billing system. While multiple services can be associated to an account, usually one account will have only one customer. For competitive pricing, some service providers are offering family level accounts, where different users are linked to a consoli- dated account for generating a single bill. 2. Service: Any tangible or nontangible offering from a service provider for which the customer is billed makes up the service. The package that is offered as a service varies based on the service provider. 3. Plan: This is a bundle of services mapped to a pricing schema. The customer is offered various plans by the service provider from which the customer selects a plan to be mapped to the account. The account is billed based on the selected plan. 4. Call detail record (CDR): This record is generated by the exchange switch with details of the call between source and destination. CDRs have valuable information about the call that can be used for billing. 5. Recurring charge: The charge the customer has to pay periodically for a prod- uct or service offered by the service provider. 6. Billing cycle: It is the periodic cycle during which the customer is billed for the subscribed service. That is, a billing cycle can be calculated as the time interval between two bill generations. 7. Accounting cycle: In order to generate a bill, a set of accounting activities needs to be performed. The cycle for which the activities to identify charges against an account are calculated. Accounting does not involve bill genera- tion and accounting is only about tallying the customer account. Some of the billing types are: Wireline billing: The billing of utilization in a wireline network. The call records are generated at the switch or elements handling billing in the core network. Wireless billing: The billing of utilizati