Exchange of information expanded: protocol requires mutual tax information gathering and sharing, including financial institution-held data for tax administration. The Second Protocol replaces Article 28 to require competent authorities to exchange information foreseeably relevant for implementing the Agreement or administering and enforcing domestic tax laws, subject to confidentiality and use restrictions limited to persons and authorities concerned with assessment, collection, enforcement, prosecution, appeals and oversight. It obliges States to employ information gathering measures even without domestic interest, while preserving limitations where information is unobtainable under law or would disclose protected trade secrets or contravene public policy, and disallows refusal solely because information is held by banks or fiduciaries.