The new 1999-2007 Personal Income Tax Return Panel is an expanded panel that represents the Spanish population of taxpayers for that period. Its statistical design (large sample stratified by region, income level and main source of income, with minimum variance sampling that leads to income estimations with errors of less than 1‰) guarantees very precise estimations of the main variables of the Spanish Personal Income Tax. These characteristics make the Panel suitable for distribution and redistribution analysis, evaluation of tax reforms and microsimulation. The objectives of this paper are: a) to provide information on the technical characteristics of the Panel, showing its usefulness for applied economic research and its complementarity with other microdata bases; b) to compare it to other tax microdata files available in Spain; and c) to analyse its reliability in population estimates of income, tax base and tax liability.

Key words: Spanish personal income tax return panel, tax microdata, administrative records.
JEL classification: C81, C83, H24.