The Taft v. Helvering case in 1940 revolved around the issue of taxation on gifts and income. The Supreme Court was asked to determine whether a gift tax could be imposed on property transferred by one spouse to another, and if such transfer could also be considered as gross income for the recipient spouse under federal law. In this case, Mr. Taft had transferred securities worth over $1 million to his wife without receiving any consideration in return; he argued that these transfers were not taxable because they were made out of "disinterested generosity". However, the Commissioner of Internal Revenue disagreed with this interpretation. In its decision, the Supreme Court ruled against Mr. Taft's argument stating that Congress has broad powers when it comes to levying taxes under Article I Section 8 Clause 1 of U.S Constitution which includes taxing gifts between spouses as well as considering them part of their gross income for federal tax purposes.

In the dissenting opinion for Taft et ux. v. Helvering, Commissioner of Internal Revenue, 1940, Justice McReynolds argued that the majority's decision was a misinterpretation of tax law and an overreach by Congress in its power to levy taxes. He contended that income should be taxed only once when it is earned and not again when it is transferred as a gift or inheritance. The justice believed this double taxation was unconstitutional because it violated the principle of uniformity in taxation required by Article I Section 8 Clause 1 of the Constitution which states "all Duties, Imposts and Excises shall be uniform throughout the United States." In his view, taxing gifts or inheritances as income resulted in unequal treatment under tax laws since some individuals were being taxed twice on their wealth while others were not.