This paper is a non-technical discussion by an economist and lawyer, each with long international experience in taxation, of the constraints and objectives that in principle and practice shape tax policy design. After discussing the main factors traditionally taken into account by those charged with designing tax policy in any country – such as revenue, the costs of taxation, equity and fairness, administrability, and the effects of taxation on growth and other non-fiscal objectives – several additional important considerations associated with ‘globalization’ are then discussed with special attention to income taxes. The paper concludes with a brief reflection on how the ‘new world tax order’ in which countries must now develop their tax systems may perhaps develop over time.