This chapter will discuss the role of international considerations in tax design. Globalization has profound implications for tax systems. Yet major tax systems, including that of the UK, retain many features that reflect closed economy conceptions. The implications of economic openness, including assessing the costs of failing to tailor tax provisions to reflect the changing international economic environment, will be reviewed, as will the role of international agreements, and the pressures as a consequence of cooperative agreements. The chapter will outline and assess international choices embedded in the UK tax system, such as the taxation of inward and outward investors; and assess the experience and prospects for international tax cooperation, including bilateral treaties, the effects of tax havens, tax competition and the OECD initiative on harmful tax practices, coordination within the EU, and the role of the European Court of Justice.