Comptroller of the Treasury of Maryland v. Wynne, 575 U.S. 542 (2015), is a 2015 U.S. Supreme Court decision that applied the Dormant Commerce Clause doctrine to Maryland's personal income tax scheme and found that the failure to provide a full credit for income taxes paid to other states was unconstitutional.

The Commerce Clause provides: [The Congress shall have Power] To regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes;Although the text of the clause appears to be a simple grant of power to Congress, the Supreme Court has long held that the clause was intended to include a negative command prohibiting state taxation that discriminates against interstate commerce even if Congress has not acted.

[1]: 6  The office of the Comptroller of the Treasury allowed the credit against the state, but not the county, income tax and, accordingly, assessed a deficiency.

[1]: 9–10  The majority rejected arguments that those cases involved gross receipts rather than net income and corporations rather than individuals.

[1]: 13–15  In the majority's view, "the notion that the victims of such discrimination have a complete remedy at the polls is fanciful" and that "it is even more farfetched to suggest that natural persons with out-of-state income are better able to influence state lawmakers than large corporations headquartered in the State.

"[1]: 15  They also found "no merit" in the Comptroller's argument that the statute is constitutional because it was not intended to discriminate against interstate commerce because the Commerce Clause "regulates effects, not motives, and it does not require courts to inquire into voters' or legislators' reasons for enacting a law that has a discriminatory effect.

[2] In September 2015, Maryland governor Larry Hogan launched a campaign to raise awareness of the availability of tax refunds.

Hogan, who assumed office in January 2015 after the Supreme Court had heard oral arguments in the case,[4] relished that he had "the pleasure of sending refund checks.

The state estimated that if every eligible taxpayer filed to claim a refund the total amount would be $3 million annually for 2012, 2013, and 2014.