The present invention relates to systems and methods for recording usage of real-time audio, video and data communication services over packet-based networks. The present invention can collect call detail record information from a network gatekeeper and analyze the call detail record information to determine its validity. After checking validity, the invention can combine the call data with information retrieved from a customer database and store the combined record in billing database. The billing database can be accessed by modular billing modules to generate a customized invoice.