service plan Fundamentals of EMS, NMS and OSS/BSS Customer Invoicing Collection Discounts Service Rating incentives Billing record Billing data Network collection analysis Figure 20.11 Billing process. selected by the customer. This rate is applied on the service consumed to compute the customer amount due to the service provider at the end of a billing cycle. The billing system should allow easy management of customer accounts. A central- ized repository that maintains a record of customer payments will be queried and updated by the billing system. The three main processes in billing are (see Figure 20.11): 1. Invoicing and collection: This is a customer level process. An invoice is gener- ated for the customer with information on the bill amount for the subscribed service. The invoice is then sent to the customer. The bill amount is then col- lected from the customer using the deferent payment options supported by the service provider and the customer account is updated. 2. Rating and discounting: This is a service level process. A predetermined rate is applied on the service consumed to come up with the amount due for a specific service usage. On the computed amount, discounts or other rebates are applied to come up with the billable amount for which an invoice can be generated. 3. Billing data collection: This is a network level process. Service usage is calcu- lated using records generated at the network elements on which the services are offered. For simple voice service, call detail records (CDRs) make up the billing data (records) that is collected. Information in the billing data gen- erated by the network elements are processed to get usage information on which rates can be applied. Billing is no longer limited to a method of collecting money from the customer for services used. It has evolved into a process that has its own independent standards OSS/BSS Functions and can be a key differentiator for a service provider. Billing is often used as a strategic tool to get and retain business. The results of 