The invention relates to a method and a system implementing the method for arranging subscriber billing in a multi-provider environment wherein a subscriber desiring a service uses both a first network (A) and a second network (T). In order to bill the subscriber, either a tariff of the second network (T) is transmitted to the first network (A), a tariff of the first network is combined with the tariff of the second network and the subscriber is billed according to the combined tariff, or a billing identifier is generated in the first network (A) to be transmitted to the second network (T), the billing identifier is attached to billing information in both networks and the pieces of the billing information that comprise the same billing identifier are combined in order to bill the subscriber. The invention thus enables a subscriber in a multi-provider environment to be billed using a single bill.