Generally, U.S. tax law treats a partnership, including an L.L.C., as an aggregation of its partners, meaning flow-through treatment applies to the partnership’s income. However, for certain purposes, a partnership is treated as a separate entity from its partners, as if it were a corporation. As a consequence, various complicated and somewhat counterintuitive tax consequences may arise from the acquisition or the disposition of interests in a U.S. partnership or L.L.C. by a foreign member. Stanley C. Ruchelman and Daniela Shani explain the way withholding taxes are computed when a foreign member sells an interest in a U.S. partnership or L.L.C. They also address U.S. tax accounting treatment for partnerships that take in additional members after operations have been conducted for several years. To say the rules are not straightforward is a massive understatement.