EN
The purpose of this article is to synthesize the basic acts of the so-called model contract law and the relations between the solutions adopted in them and the regulation of contractual penalty applicable in Polish law. Particular emphasis was puted on the analysis of conditions for a claim for payment of a contractual penalty and acceptable limits of modification of a debtor’s liability in Polish and model law. On the basis of model law, it was proposed to resolve the most frequent doubts in Polish doctrine. The comparative conclusions drawn in relation to the contractual penalty are also an example of evaluation of the Polish regulation from the point of view of the progressing process of European private law harmonisation.