This book examines the relationship between tax law and crisis. In times of environmental, financial, and public health breakdown, policymakers look to tax for solutions. Yet these crises also constrain the ways in which tax liabilities can be imposed and administered, and limit the revenues that can be collected. What should governments do in these circumstances and what are the wider consequences for states, societies, and institutions such as the EU? The book shows how crises place strain on the basic functions of tax, including revenue-raising, institution-building, regulation, redistribution, and the structuring of society. These strains bear more heavily on some sections of business and society than others. This makes the tax consequences of crisis unpredictable. It also means that the best choice of legal response is not merely a technical matter. Instead, it engages deeper attitudes towards crisis relief, change, social values, and democratic control. These issues are highlighted by COVID-19 but are of utmost lasting importance. The book takes a comprehensive approach and looks in more depth at the systemic roles that crises play in contemporary tax systems. It features an impressive cast of leading researchers across multiple jurisdictions and is essential for policymakers and scholars alike.