The international tax problems of today are typically beyond the scope of a single nation to solve. However, the prospect of multinational problem solving, often under the auspices of an international organization, unleashes objections grounded in sovereignty. Despite widespread reliance on sovereignty arguments, little attention has been directed at what precisely is meant by sovereignty and what place it has in international tax policy. This article contends that a loss of sovereignty undermines both significant functional roles played by a nation-state (revenue and fiscal policy) and important normative governance values (accountability and democratic legitimacy). Whether these limitations are severe enough to demand that a sovereign state recall its taxing powers from an international body (or not surrender them initially) depends on the nature of the powers in question and the necessity for a coordinated global response. Part I develops the basic nexus between sovereignty and taxation. Part II examines the use of sovereignty in the debates and analyses surrounding three international tax case studies. Drawing upon the case studies, Part III considers how sovereignty claims are manipulated in tax debates, how states think about sovereignty in taxation, and what their decisions, in turn, suggest about the future of international tax and the prospects for international cooperation.