Complete Auto Transit, Inc. v. Brady, 430 U.S. 274 (1977), is a United States Supreme Court case regarding the Commerce Clause and sales tax.

Complete Auto paid the taxes of $122,160.59 under protest, and then undertook a refund action in the Chancery Court of the First Judicial District of Hinds County.

[2]Complete Auto argued against the constitutionality of tax, stating that they were part of an interstate operation, involved in transporting vehicles from the factories in Michigan to the dealers in Mississippi.

The ruling established a four-prong test for constitutionality of a tax under the Commerce Clause:[3] Even though Complete Auto asserted that it was a part of an interstate operation, the Court agreed with Mississippi that while operating within the state, it was afforded services, such as police protection, provided for by taxation.

The test enunciated in Complete Auto Transit received significant interpretation in Commonwealth Edison Co. v. Montana, 453 U.S. 609 (1981).