The Polish government – Council of the European Union interoperability is an important factor of the Europe enlargement success. This article presents how the interoperability has been achieved and further exploited in the European Exchange of Documents – Poland (EWD-P) system – an application responsible for elaboration of the official Polish standpoint concerning adjustment of the newly associated states law to the EU procedures and regulations. The mechanisms and the role of the underlying platform for knowledge management intensive portals development are presented.