A billing method and billing system to determine usage fees which are charged to the user of a digital telecommunications network, whereby a usage fee charged for a connection is determined prior to establishing this connection from statistical characteristics of previous connections of the user, is described. Usage fees are determined from a dynamic client profile, derived from one or multiple random variables of previous connections of the user, which is stored in memory and rederived after each new customer connection. In a simple variant, the client profile contains a value proportional to the average price per connection or to the average duration of a connection of the user. The random variables used to derive the client profile include, for example, the connection duration, the time of day, the day of the week, and/or geographic characteristics of previous connections.