This chapter first sketches the impact of three different kinds of tax competition (for portfolio capital, so-called paper profits, and foreign direct investment (FDI)) on the de facto sovereignty of states. It shows how tax competition exacerbates social inequalities in order to explain why it is a case of background injustice. The chapter then lays out two principles of international taxation: a membership principle and a constraint on fiscal policy that rules out fiscal arrangements. Next, the chapter proposes the establishment of an International Tax Organization (ITO) and endorses unitary taxation with formulary apportionment (UT+FA) as a reform of corporate taxation. The chapter also discusses the objection that these principles are incompatible with defending a cosmopolitan theory of global justice. Furthermore, it argues that the two principles serve as a normative toolkit to specify to what extent the interdependence of states in fiscal matters calls for normative interdependence.