Mayo Foundation for Medical Education and Research v. United States

Holding

Treasury Regulations are entitled to Chevron deference; the prior National Muffler standard does not apply uniquely to tax regulations.

Facts

Mayo challenged a Treasury regulation excluding medical residents from the student FICA exemption.

Reasoning

Chief Justice Roberts held that there is no reason to apply a less deferential standard to tax regulations than to other agency regulations under Chevron. The decision substantially strengthened Treasury's regulatory authority in tax matters.