The present invention relates to a system and method for determining whether playing has been performed, determining the number of times that the playing has been performed, and charging fees based on the determination results (hereinafter "post-payment") after music has been provided from an on-line sound source server and has been played in users' players, such as MP3 players, so as not only to charge the users fees for multimedia files in a post-payment manner, not in a convention advance payment manner but also to overcome the problems of a conventional method of charging fees at the time when users access an on-line source server and download or play music (hereinafter "advance payment"). In particular, the present invention relates to a post-paid billing system and method wherein multimedia files are first provided to the user and fees are charged based on the number of times (including first playing that is related to the determination of whether playing has been performed) the users have played the provided multimedia files. According to the present invention, the users can play and enjoy the multimedia files at a lower price. Since the fees are clearly and correctly charged, the profit distribution between service providers and multimedia copyright holders can be easily made, whereby the copyright holders can earn the royalties. Since the multimedia files can be freely duplicated/distributed, the copyright infringement due to unauthorized duplication can be basically prevented, whereby the development of multimedia industry can be promoted.