The following paper set out to reflect on the meaning of the ne bis in idem principle as regards the new regulation of continuous act. It presents the consequences of applying the concept of continuous act enshrined in Article 12 of the Criminal Code to cases encompassing previously imputed misdemeanors against property. Such an application of Article 12 – according to its literal wording – can lead to two-tier, sequently realized criminal liability of the perpetrator for the same act. Thus, the article includes an analysis of the appropriate way of determining the identity of an act (idem) as a fundamental, basic element actualizing the prohibition of repeated punishment. Under the current ECHR and ECJ case law, Polish law enforcement and judicial authorities are bound by their interpretation of the ne bis in idem principle. Consequently, the authors are of the opinion that the aforementioned established interpretation of ne bis in idem effectively excludes the possibility of applying the new Article 12 concept so as to hold a perpetrator criminally liable for two or more previously imputed misdemeanors.