This article analyses through concept of income inequality gap impact of economic policy on reducing income inequality in society. Income inequality gap presents a difference between levels of income inequality measured on gross money income data and net money income data. This gap is determined by specific areas of social policy, concretely this gap considers on a system of mandatory contributions and income taxes. Via this income inequality gap we can measure success of redistribution function of economic policy that means the success of social poli-cy in reducing income inequalities in society. If the difference between lev-els of both income inequalities is low we can assume about not very effective re-distribution function of economic-social policy and vice versa. Mathematically is the income inequality and income inequality gap expressed and measured by the method of non-weighted average absolute deviation. The article would be rather theoretical focused but is supplemented by practical example of analysis of income inequality gap based on data for on data for Czech Republic from years 2005-2015.