The contribution deals with the current jurisprudence of European courts and the subsequent jurisprudence of domestic courts, which introduced conditions under which it is possible not only to conduct tax and criminal proceedings on the same act of the same person simultaneously, but also to impose a criminal sanction in both proceedings. The author's attention is focused on the analysis of the jurisprudence in question and its effects from the point of view of one of the basic principles of criminal proceedings ne bis in idem.