In the case of Helvering, Commissioner of Internal Revenue v. Pfeiffer (1937), the United States Supreme Court ruled on a matter related to income tax law. The issue at hand was whether or not an individual could claim a deduction for losses incurred from selling securities if those securities were purchased with borrowed money and then sold at a loss. The court held that such losses are deductible under Section 23(e) of the Revenue Act of 1928, which allows deductions for "losses sustained during the taxable year and not compensated by insurance or otherwise." This decision clarified that even though Mr. Pfeiffer had used borrowed funds to purchase these securities, he still suffered an economic loss when he sold them for less than their cost price; therefore, this loss is deductible under U.S income tax law.

The dissenting opinion in the case of Helvering v. Pfeiffer argued that the majority's decision to tax Mrs. Pfeiffer on her entire annuity income was incorrect and unfair. The dissenters believed that only a portion of this income should be taxed, as part of it represented a return on capital which had already been subjected to taxation when initially earned by Mr. Pfeiffer during his lifetime. They contended that taxing all annuity payments without considering their source would result in double taxation, which is contrary to established principles of equity and fairness in tax law.