At the heart of the doctrine is what the court calls the “unitary business principle,” which requires before a state can impose its tax, a finding that the company’s in-state operations are part of a unified whole. The hallmarks of a unitary business, the court has held, are “functional integration, centralized management and economies of scale.”
The question for the court on Tuesday was whether an alternative route existed for states to capture revenue from businesses that were not unitary. The Supreme Court had raised this possibility with a passing reference in a 1992 opinion to tax liability generated by assets that served an “operational rather than an investment function” in a business. That ambiguous reference led some state courts to conclude that the justices had blessed an “operational function” test that paved the way to taxing multistate companies that did not qualify as unitary businesses.
That was an erroneous extrapolation, the high court said in an opinion by Justice Samuel A. Alito Jr. The earlier references to “operational function,” he said, “were not intended to modify the unitary business principle by adding a new ground” for taxation. Regardless of the details of a parent company’s relationship to its subsidiaries, the business had to be found unitary in the first place before a state could tax a part of the revenue.