A contractual penalty is a substantive legal institute that is also important from a procedural point of view (as a separate property claim). In particular, the Supreme Court of the Czech Republic has repeatedly addressed the issues of defining a contractual penalty in an action, maturity or limitation of the right to payment of a contractual penalty, as well as determining the correct court fee, reducing the contractual penalty by a court (as a moderating right), and the relationship of contractual penalty to the interest on late payment or to the damages.
The aim of the paper is to analyze the contractual penalty in a procedural context and to draw attention to some difficulties that courts face in their decision-making practice.