DT: Soviet Union: double taxation agreement, Article 23: Exchange of information
(1) The competent authorities of the Contracting States shall, to the extent permitted by their respective laws, exchange such information as is necessary for the carrying out of this Convention and of the domestic laws of the Contracting States concerning taxes covered by this Convention insofar as the taxation thereunder is in accordance with this Convention.
(2) In no case shall the provisions of paragraph (1) of this Article be regarded as imposing on the competent authority of either Contracting State the obligation:
(a) to carry out administrative measures at variance with the laws or administrative practice prevailing in either Contracting State;
(b) to supply information which is not obtainable under the laws or in the normal course of the administration of either Contracting State;
(c) to supply information which would disclose any industrial, commercial or professional secret or process, or information, the disclosure of which would be contrary to public policy.
(3) The competent authorities of the Contracting States shall supply to each other details of any substantial changes which are made in their respective taxation laws.
(4) Any information exchanged under the provisions of this Article shall be treated as secret and shall not be disclosed to any persons other than persons concerned with the implementation of the laws relating to the taxes covered by this Convention.