The aim of this study is to present the case law of the Court of Justice of the European Union (CJEU) regarding the admissibility of parallel punishments in proceedings conducted separately before criminal courts and administrative authorities. Pursuant to Article 50 of the Charter of Fundamental Rights of the European Union, no one shall be liable to be tried or punished again in criminal proceedings for an offence for which he or she has already been finally acquitted or convicted within the Union in accordance with the law (the ne bis in idem principle). According to the CJEU, this principle does not constitute a legal obstacle to the application of sanctions for the same unlawful conduct of the same person in both criminal and administrative proceedings, if the sanction imposed by the administrative authority does not have the nature of a criminal penalty (the case C-617/10 Fransson). Assessment of such a nature in accordance with the case law of the CJEU (influenced by the judgment of the European Court of Human Rights in the Engel case) needs to be based on three criteria: the classification of a given procedure in domestic law, the existence of a repressive function of the measure adjudicated under the procedure and the degree of its severity (the case C-489/10 Bonda). In the opinion of the CJEU, the ne bis in idem principle mentioned in Article 50 of the Charter is also not absolute, because the restrictions on the use of the rights granted by the Charter are allowed pursuant to Article 52 (1) of the Charter. Therefore, according to the CJUE, it is possible to double sanction a given behaviour with measures of a penal nature, if it is justified by general objectives such as the protection of the tax system or of the regularity of stock exchange trading, provided that each of the proceedings performs its own specific additional objectives and that the accumulation of sanctions is based on the principle of proportionality. While administrative sanctions could be meant to counteract any transgressions, criminal sanctions should be limited to the most serious, culpable abuses. Moreover, the Member States should regulate the mutual influence of both proceedings, so as not to punish too severely the same behaviour and so that the sanctions applied jointly are absolutely necessary (the case C-545/15 Menci, the case C-537/16 Garlsson Real Estate and Others). On the other hand, according to the CJUE, Article 50 of the Charter excludes the possibility of bringing a given entity to administrative responsibility in the event that it had already been legally acquitted of committing the same offence with a final court ruling, because the acquittal judgement definitively determines that no act has been committed, and thus it is pointless to consider whether an exception to the ne bis in idem principle in such a case is justified in the light of Article 52 (1) of the Charter (joint cases C-596/16 and C-597/16, Enzo Di Puma and Consob). Finally, the CJUE states that Article 50 of the Charter must be interpreted in such a way that it does not preclude the application of the national provision which allows for conducting criminal proceedings, if a definitive administrative penalty for the same acts has been imposed on a company with a legal personality and criminal proceedings have been initiated against a natural person (joint cases C-217/15 and C-350/15, Orsi, Baldetti).