This chapter discusses the application of human rights law to state tax policy, identifying normative principles by which UN human rights treaty supervisory bodies—like the Committee on Economic, Social and Cultural Rights—can assess whether a state’s tax laws and practices comply with its human rights obligations. In a human rights perspective, state tax policies can be improved in four directions: widening the tax base to finance public services, ensuring progressivity to reduce inequalities, plugging holes in the tax system, and strengthening participation and accountability around tax policy. The chapter then argues that the progressivity of a state’s fiscal policy depends on not only how tax revenues are raised but also how they are spent. It also provides an overview of recent literature on the impacts of tax policy on investment decisions, and traces recent international efforts to curb illicit financial flows.