Advanced VoIP Billing System can be used with RADIUS servers and also it can be used with switches which produce CDR's directly. Advanced VoIP Billing System can be used with any RADIUS server which supports the VoIP functionality and provide the ability to define the structure of authentication and accounting tables for example Advanced Radius. Advanced Radius supports Cisco and Quintum at this moment. Both prepaid and postpaid billing schemes are supported. Postpaid users don't get locked where advance or prepaid users get disconnected and locked when ever their current balance becomes less than their credit limit. Usually prepaid users have credit limit zero.Complete invoices system is provided, invoices can be generated automatically and manually, and can be sent to users through emails. Also users can see their old and pending invoices online. In prepaid calling cards module prepaid (scratch) cards are generated, activated and sold to dealers or locations (outlets of an ISP). The complete information about cards, dealers and location is maintained. Call intervals are provided, where call interval time is defined in seconds and rate as amount. For example first call interval is of 30 seconds and its rate is $.5 then even if call is of less than 30 seconds, $.5 will be charged. And Second interval is of 60 seconds with rate $1 and total time of call is 35 seconds then it will be charged $1.5. Different rates can be defined for same destination. In this way different plans can have different rates and these plans are assigned to users. We have provided the functionality by which almost all kind of Credit Card payment gateways are supported, for example Authorize.Net, LinkPoint, PaymentsGateway.Net, Bank of America eStores, Verisign, Worldpay and PayPal.