Substance over form: tax consequences follow true legal substance where arrangements lack commercial substance, per anti-avoidance law. An arrangement lacks commercial substance under Section 97(1)(a) when the substance or effect of the arrangement is inconsistent with, or significantly differs from, the form of its steps; Clause (a) codifies the substance v. form doctrine, requiring tax consequences to be assessed on the real substance, and permitting tax authorities to unravel devices and determine the true legal relations when form masks substance.