Lack of commercial substance can trigger GAAR, denying tax benefits where arrangements mask funds or use accommodating parties. An arrangement is deemed to lack commercial substance under Section 97(1)(b) where it includes round trip financing, an accommodating party, elements that offset each other, or disguises the value, source, location, ownership or control of funds. Round trip financing covers series of transfers lacking substantial commercial purpose apart from tax benefit, irrespective of traceability or sequence. An accommodating party participates mainly to secure a tax benefit for the taxpayer. Such features permit disregarding intermediaries, reattributing income, denying treaty benefits, and disallowing related deductions.