Exchange of Information expanded to require cross-border tax data sharing, including bank-held and fiduciary information, subject to confidentiality. Article 27 replaces the prior exchange regime with a broad mutual assistance obligation: competent authorities must exchange foreseeably relevant information for tax administration and enforcement; received information is to be treated as secret and used only for specified tax purposes unless both States permit broader use and the supplying State authorises it; limitations do not permit refusal solely because information is held by banks, nominees or fiduciaries, and States must use their information gathering measures even absent domestic need.