Many people assume that an individual who receives a Schedule K-1 from an entity must be a partner of that entity. The law of "tax estoppel" is not so simple. In fact, a string of decisions, including the First Department's recent decision in Tradesman Program Managers v. Doyle, 202 A.D.3d 456 (1st Dept. Feb. 3, 2022) (Tradesman), have held that issuance of a K-1 alone is not determinative of partnership. Since partnership disputes often involve threshold questions of whether a partnership interest exists, this article provides a detailed look at New York's tax estoppel doctrine and the various exceptions recognized by New York courts.