The article attempts to define the essence of the personal income tax (PIT) system. Should it be progressive or proportional? The arguments in favour of replacing the now in force progressive scale by a proportional personal income tax are presented. Critical assessment of the progressive scale is followed by a substantiation of purposefulness of maintaining the progressive PIT system. The inadequacy of the PIT scale in force at present in Poland is pointed to, especially when the principle of the capacity to pay taxes, that is regarded as the main criterion of just distribution of tax burden, is taken into account. In the next part of this article the evolution of the government plans to reform the personal and corporate income tax system is discussed and critical remarks concerning those plans are formulated. The last part contains the most important conclusions derived from the analysis.