In this course, we will look at four Supreme Court cases, with relevance in our day-to-day practice. We will discuss Welch, defining ordinary expenses; Gilmore, regarding legal expenses, Arrowsmith, involving the matching concept; Boyle; on appropriateness of penalties; Groetzinger, defining a trade or business; Duberstein, which differentiates a gift from income subject to taxation; Generes, discussing business bad debt from non-business bad debt; and what Indopco tells us about capitalization, in light of the new repair regulations.