While the O.E.C.D. and the European Commission have only recently discovered the “principal purpose” test as a tool to combat aggressive tax planning, U.S. case law has enforced an economic substance rule for over 85 years and that rule was codified in 2010.  Fanny Karaman, Neha Rastogi, and Stanley C. Ruchelman explain the hurdles that must be achieved in order for a plan to have economic substance.