The paper studies the effectiveness of tax amnesties and their impacts on capital taxation and public spending. We leverage rich policy variation from Argentina, which implemented the world’s most successful program, reportedly revealing assets worth 21% of GDP. First, despite substantial offshore tax evasion, declared foreign assets quadrupled. Second, tax progressivity improved because disclosures were extensive among the wealthiest 0.1%. Third, improving tax compliance has sizable fiscal externalities on capital taxes and social transfers: the wealth and capital income tax bases more than doubled, and the earmarked revenue boosted pension benefits by 15%. We end by discussing the lessons from Argentina.