The main purpose of the professional VoIP billing system - Voice Clerk by NG Systems is to charge and limit the calls of a certain company's employees, aiming at the optimization of the expenses for phone calls in its inner infrastructure. The system allows collecting and storing information about the committed incoming and outgoing calls, trough the organization, calculating their cost, blocking or notifying the users, who have reached an administratively assigned limit and generating a variety of different reports about the expenses. Unlike the other existing systems on the market today, the incoming data about the calculations is received from the VoIP router, that manages the incoming and outgoing calls (via the RADIUS protocol) or it can be gathered directly from the Call Data Record (CDR) database of Cisco Call Manager™ (CCM).