The aim of this article is to assess the degree of the implementation of the best practices concerning tax rulings developed under Action 5 of the BEPS Project in Polish tax law. The authors present the current situation of Poland's tax ruling system. Then, the authors assess the degree of implementation of each best practice. The authors also formulate critical comments on the OECD's best practices. In the opinion of the authors, the Polish tax ruling regulation generally meets most of the OECD's requirements, primarily because it is a fully transparent system.