In 2013, Spain's tax revenue was 32.6 % of GDP. Compare that to Germany 36.7 %, Netherlands 36.3 % and Finland 44.0 %. Also consider that these as proportion of tax revenue to official GDP, and it's pretty safe to assume that Spain has more in grey economy (not in official statistics) than northern Euro countries.
http://stats.oecd.org/index.aspx?DataSetCode=REV
In 2013, Spain's tax revenue was 32.6 % of GDP. Compare that to Germany 36.7 %, Netherlands 36.3 % and Finland 44.0 %. Also consider that these as proportion of tax revenue to official GDP, and it's pretty safe to assume that Spain has more in grey economy (not in official statistics) than northern Euro countries.