In the first half of 1999, KPN submitted proposals to the Commission of OPTA for a change of charges for calls originating in the fixed network and terminating at phones in mobile networks. KPN’s proposals concerned the tariffs for terminating calls to subscribers in any mobile network. The Commission of OPTA is statutorily required to assess whether proposed tariffs changes are in accordance with the requirements of cost orientation. It found there was no agreement between KPN and one mobile provider on the call termination charges and the proposed end-user tariffs. Furthermore, the amount that KPN charged in the end-user tariff for the use of its own network, was disputed. These are some of the reasons why the Commission now considers it desirable to give a more detailed interpretation of the way in which “fixed to mobile” charges are assessed on cost orientation.