This book provides a comprehensive survey of optimal income tax theory, following the development of research strategy from the basic Mirrlees model through to its refinements, examining how optimal tax rates and the shape of tax schedules are affected by new considerations. Optimal tax theory has an important contribution to make to tax policy formation, and has become especially pertinent in recent years with the renewal of controversy over whether progressive income tax is in fact desirable or not. The author not only covers the historical background and modern formulations of the theory, but extends his discussion to consider the most important extensions of the model and the interrelation of income tax with other instruments of tax and expenditure policy.

From the 1980s onward, income inequality increased in many advanced countries. It is very difficult to account for the rise in income inequality using the standard labour supply/demand explanation. Fiscal redistribution has become less effective in compensating increasing inequalities since the 1990s. Some of the basic features of redistribution can be explained through the optimal tax framework developed by J. A. Mirrlees in 1971. This Element surveys some of the earlier results in linear and nonlinear taxation and produces some new numerical results. Given the key role of capital income in the overall income inequality, it also considers the optimal taxation of capital income. It examines empirically the relationship between the extent of redistribution and the components of the Mirrlees framework. The redistributive role of factors such as publicly provided private goods, public employment, endogenous wages in the overlapping generations model and income uncertainty are analysed.

Tax systems raise large amounts of revenue for funding public sector's activities, and tax/transfer policy, together with public provision of education, health care, and social services, play a crucial role in treating the symptoms and the causes of poverty. The normative analysis is crucial for tax/transfer design because it makes it possible to assess separately how changes in the redistributive criterion of the government, and changes in the size of the behavioural responses to taxes and transfers, affect the optimal tax/transfer system. Optimal tax theory provides a way of thinking rigorously about these trade-offs. Written primarily for graduate students and researchers, this volume is intended as a textbook and research monograph, connecting optimal tax theory to tax policy. It comments on some policy recommendations of the Mirrlees Review, and builds on the authors work on public economics, optimal tax theory, behavioural public economics, and income inequality. The book explains in depth the Mirrlees model and presents various extensions of it. The first set of extensions considers changing the preferences for consumption and work: behavioural-economic modifications (such as positional externalities, prospect theory, paternalism, myopic behaviour and habit formation) but also heterogeneous work preferences (besides differences in earnings ability). The second set of modifications concerns the objective of the government. The book explains the differences in optimal redistributive tax systems when governments - instead of maximising social welfare - minimise poverty or maximise social welfare based on rank order or charitable conservatism social welfare functions. The third set of extensions considers extending the Mirrlees income tax framework to allow for differential commodity taxes, capital income taxation, public goods provision, public provision of private goods, and taxation commodities that generate externalities. The fourth set of extensions considers incorporating a number of important real-word extensions such as tagging of tax schedules to certain groups of tax payers. In all extensions, the book illustrates the main mechanisms using advanced numerical simulations.