http://www.worldwide-tax.com/poland/poland_tax.asp
From the FlatTax-Blosspot:
"In Poland the governing coalition under the leadership of Prime Minister Donald Tusk favors a flat tax, but the leading opposition party holds the office of president with the power to veto legislation. If and when Tusks party wins control of both parliament and the presidency, Poland will be poised to adopt a 19% flat tax on individuals to complement its 19% corporate tax."
The Law and Justice party, which is more religious and socially conservative, is the more socialist of the two.