In this paper, we use administrative data on tax returns to characterize the distributions of before-and after-tax income, tax liabilities and tax credits in Spain for individuals and households. We use the most recent available data, 2015 for individuals and 2013 for households, but also discuss how the income distribution and taxes have changed since 2002. We also estimate effective tax functions that capture the underlying heterogeneity of the data in a parsimonious way. These parametric functions can be used to calculate after-tax incomes in surveys where this information is not directly available, and can also be used in quantitative work in macroeconomics and public finance. Keywords Personal income tax • Tax functions • Income distribution JEL Classification E62 • H24 • H31 We thank the editor, two anonymous referees, and seminar participants at Banco de España, the Workshop on Fiscal Policy and Microsimulation (Valencia), the Workshop on Microsimulation and Fiscal Policy (Banca d'Italia), the 43rd Simposio de la Asociación Española de Economía-Spanish Economic Association (SAEe, Madrid), and the Conference SERIEs-Banco de España "Taxes and Transfers" for comments and discussions. The views expressed in this paper are those of the authors and do not necessarily coincide with the views of the Banco de España or the Eurosystem. Guner acknowledges financial support from the Spanish Ministry of Economy and Competitiveness, Grant ECO2014-54401-P.