Exchange of information: Contracting States must share foreseeably relevant tax information subject to secrecy and narrow exceptions. Article 27 requires Contracting States to exchange foreseeably relevant information (including documents or certified copies) for administering taxes covered by the Agreement, subject to confidentiality and use limitations. Received information must be treated as secret and used only for assessment, collection, enforcement, prosecution, or appeals, with permitted disclosure in public court proceedings. Narrow exceptions prevent compulsion of measures contrary to domestic law or administrative practice, the supply of unobtainable information, or disclosure of trade secrets or information contrary to public policy. States must use available information-gathering measures even if they lack a domestic interest, and cannot refuse solely because information is held by banks, nominees, agents or fiduciaries or relates to ownership interests.