Exchange of information: competent authorities must share tax relevant data with strict confidentiality and limited use. The Article requires competent authorities to exchange information foreseeably relevant for implementing the Convention or administering domestic tax laws, with such information to be treated as secret and disclosed only to persons or authorities concerned with assessment, collection, enforcement, prosecution, appeals or oversight, and used only for those purposes unless both States lawfully permit other use and the supplying State authorises it. It limits obligations by excepting measures contrary to domestic law or practice, information not obtainable in the normal course, and trade or public policy secrets, while obliging States to use their information gathering powers even without a domestic interest and prohibiting refusal solely because information is held by financial intermediaries or concerns ownership interests.