Exchange of information: treaty requires mutual tax information sharing with confidentiality and limits on disclosure. The Protocol replaces Article 26 with a comprehensive Exchange of Information provision requiring competent authorities to exchange foreseeably relevant information, including documents or certified copies, for implementing the Agreement or administering domestic tax laws. Exchanged information is to be treated as secret and disclosed only to specified authorities for assessment, collection, enforcement, prosecution, appeals or oversight and used only for those purposes unless both States' laws and the supplying authority permit other uses. Limitations prohibit requests that violate domestic law, seek unobtainable documents, or reveal trade secrets or public policy contrary information, but bank secrecy or fiduciary status alone does not permit refusal to supply ownership information.