Why are tax systems so complex? What are the causes of tax law complexity? What are the consequences? Why is tax simplification so difficult to achieve? These, and related questions, lie at the core of this volume on tax simplification featuring chapters by leading tax experts around the world. The quest for simplicity – or at least some move towards simplification – has been a fixation of governments and others for many years, but little appears to have been achieved. Tax simplification is the most widely quoted but the least widely observed of the usually stated goals of policy (equity and efficiency being the others). It has been used (and abused) as a primary justification for tax reform over the last century, and typically it is seen as ‘a good thing’ – to say that one is in favour of tax simplification is tantamount to stating that one is in favour of good as opposed to evil. The volume explores all aspects of tax complexity and simplification, from policy through law to practice. It is both theoretical and practical, providing key insights that can help the reader to understand tax complexity, assess its impact and identify potential means by which tax simplification can be attained – or at least complexity can be contained. The contributors to the volume cover a range of topics including: theoretical perspectives explaining tax complexity; ideological underpinnings of tax complexity; causes of tax complexity; ways of measuring tax complexity; tax compliance costs studies; institutional monitoring of tax complexity; implications of complexity for judicial review; the role of vested interests; administrative and technological drivers of tax simplification; and institutional and other pathways towards improved simplification. Contributors include eminent academics, administrators and practitioners with direct knowledge of the adverse consequences of tax complexity and of how simplification initiatives have fared in a variety of countries from around the world. Attempts at tax simplification have – thus far – not been particularly successful. This in-depth study, backed up with facts, evidence and soundly based recommendations of how simplification may be achieved, will be of critical concern for all tax system stakeholders; taxpayers, tax advisers, tax legislators and policy makers, tax administrators and a range of other commentators including academics and journalists.