Exchange of information: treaty requires mutual sharing of tax relevant documents while protecting confidentiality and use limits. The treaty obliges competent authorities to exchange information foreseeably relevant to implementing the Agreement and related domestic tax laws, including documents, with received information treated as secret and limited to persons and authorities handling assessment, collection, enforcement, prosecution or appeals. Use for other purposes requires legal permissibility in both States and supplier authorisation. Limits prevent requiring changes to domestic law or production of unobtainable information, or disclosure of trade secrets or information contrary to public policy. Requested States must employ information gathering measures even without domestic interest and cannot refuse solely because information is held by financial intermediaries or concerns ownership interests.