The European Union (EU) tax mandate remains narrow. That there was only a limited transfer of tax authority to the EU exemplifies the failure of political and fiscal integration. Using a political economy framework, this article analyzes why the heads of state rejected tax harmonization proposals in the intergovernmental conferences. The presented findings of the original data on the Maastricht, Nice and Lisbon negotiations support the main hypothesis derived from the theoretical framework – namely that resistance against tax harmonization came predominantly from low-tax countries. Moreover, the results indicate that after the accession of the central and eastern European countries the prospects of harmonizing tax policy starkly decreased. The analysis shows that tax heterogeneity and the enlargements have negative effects on tax integration. Based on the empirical findings and the theoretical framework, the article concludes by discussing how the creation of the monetary union restructured the politics of tax Europeanization and fiscal integration.