Presumptive taxation raises both theoretical and practical issues of great importance. From a policy perspective, the most interesting issue is probably to what extent presumptions can be used to simplify the task of administration without fundamentally changing the tax base. From a practical perspective, the fundamental issue raised by presumptive taxation is the trade-off between accuracy and administrability. Using presumptions improves the administrability of a tax while lowering its accuracy, and the question is to what extent the former benefit justifies the latter cost. A related issue is whether presumptive taxation should be considered a permanent supplement to, or even replacement for, the more traditional tax system, or whether it should be viewed as merely a transitional phase until the tax administration is capable of collecting the normal tax without the widespread use of presumptions. The papers collected in this volume reflect the broad diversity of types of presumptive taxation in use today. The overall theme of these papers is that presumptive taxation is a widespread form of taxation, not limited to developing countries, which can be helpful whenever administering the normal tax base is too challenging.