The article aims to identify the impact of changes in tax and benefit regulations—introduced in Poland from 2006 to 2010—on household income distribution. A wide range of legal adjustments in income policy motivated this research agenda. The research method used is based on the decomposition of changes in income distribution and poverty indexes onto those that may be attributed to changes in the distribution of income and those caused by the tax and benefit adjustments. The so-called Shapley values for hypothetical disposable incomes generated by the different regulation systems were calculated in the article. The hypothetical incomes were simulated using the SIMPL tax and benefit microsimulation model. The study confirmed that changes in income distribution have a greater impact on the threat of poverty than those caused by regulatory adjustments. The results of the analysis indicate that in the 2006-2010 period, which was a time of relatively fast economic growth, more care was taken to enhance financial motivation to work than to reduce income inequalities. Despite a strong pro-efficiency policy, regulatory changes effectively protected the poorest households, as shown by changes in the poverty indexes.