Exchange of information obligates cross-border tax information sharing while preserving confidentiality and limited legal exceptions. Article 28 requires competent authorities to exchange foreseeably relevant information, including documents, for administering the Convention and domestic tax laws; such information must be treated as secret and used only for tax assessment, collection, enforcement, prosecution, appeals or oversight unless both States' laws and the supplying authority allow other uses. The Article limits the obligation where information is unobtainable, would require changing domestic laws or administrative practices, or would disclose trade secrets or violate public policy, but obliges States to use their information gathering measures even when they lack a domestic interest, and excludes bank or fiduciary status as a sole ground for refusal.