In determining whether the commerce clause of the U.S. Constitution prohibits a state’s taxation of a remote seller, the U.S. Supreme Court for decades has upheld a tax if (1) there is a substantial nexus between the taxing state and the taxpayer; (2) the tax is fairly apportioned; (3) the tax does not discriminate against interstate commerce; and (4) the tax is fairly related to the taxing state’s provision of services to the taxpayer.[1]

What kind of nexus is substantial enough to allow a state to tax a business’s sales in interstate commerce? In its 2018 decision in South Dakota v. Wayfair, Inc., the U.S. Supreme Court held that a business’s physical presence in the taxing state is not required.[2] Describing the remote-seller litigants as “large, national companies that undoubtedly maintain an extensive virtual presence,” the Court held that substantial nexus was clear in view of “both the economic and virtual contacts” that the remote-seller litigants had with South Dakota.[3] The U.S. Supreme Court recited the general rule that substantial nexus exists when a taxpayer has availed itself of the substantial privilege of carrying on business in the taxing state, and it appeared to describe “virtual contacts” and “virtual presence” as follows: “Between targeted advertising and instant access to most consumers via any internet-enabled device, ‘a business may be present in a State in a meaningful way without’ that presence ‘being physical in the traditional sense of the term.’”[4] Wayfair left many questions unanswered, including whether (and, if so, how) “virtual contacts” and “virtual presence” may be required for a substantial nexus to tax in compliance with the commerce clause.