General Anti-Avoidance Rule targets arrangements with main purpose of securing tax benefit, permitting denial of tax or treaty advantages. GAAR empowers tax authorities to declare arrangements impermissible where the main purpose is to obtain a tax benefit and one or more indicia are met, such as non-arm's-length rights, misuse of tax provisions, lack of commercial substance, or non-ordinary implementation. Once declared impermissible, the statute permits denial of tax or treaty benefits and making of assumptions and adjustments; procedural safeguards include vetting by senior authorities and an approving panel, and specific exclusions and grandfathering rules apply in prescribed circumstances.