The U.S. Supreme Court case Commissioner of Internal Revenue v. Culbertson et ux., 1948, centered on the issue of income tax liability for a family partnership business. The Culbertsons were involved in a cattle ranching operation and had formed several partnerships within their family to manage different aspects of the business. The Commissioner of Internal Revenue argued that these partnerships were not genuine and should be disregarded for tax purposes, which would result in higher taxes owed by individual members of the family. The Supreme Court disagreed with this assessment, ruling that whether or not a partnership is real for tax purposes depends on whether parties intended to join together as partners in conducting the enterprise; it does not solely depend on factors such as capital investment or legal title ownership but rather an overall evaluation about intent and conduct. This decision established what became known as "the Culbertson test," providing guidance for future cases involving similar disputes over taxation related to familial businesses structured as partnerships.

In the dissenting opinion for Commissioner of Internal Revenue v. Culbertson, Justice Rutledge disagreed with the majority's decision to overturn a lower court ruling that had found in favor of the IRS. He argued that there was no clear evidence showing an intent to form a partnership between Culbertson and his sons beyond tax avoidance purposes. The justice believed that family relationships should not automatically imply genuine partnerships for tax purposes, especially when there is little proof of shared financial risk or managerial control among all parties involved. In his view, this could potentially open up avenues for widespread abuse where families might set up pseudo-partnerships merely as means to evade taxes rather than engage in legitimate business operations together.