This article is based on literature analysis and selected law regulations typified in the XXXIV section of the Penal Code titled Offence Against Reliability of Documents. In the introductory paragraph the authors present the social perspective of forgeries in documents which may affect the confidence granted to official and private documents. This subject chosen for research is a very current one because the forgeries in documents are very popular illegal activities. They also discuss theoretical aspects of the legal definition of the document and show various aspects of the Article 271 of the Penal Code for instances the subject and forms of the criminal offences, procedures and sanctions. Besides the theoretical aspects in the last section were analyzed the examples of judicial practice. In this thesis the authors mainly used analytical method so necessary for understanding details criminal offences of forgery in documents stipulated by art. 271 of the Penal Code. The sources which were used are mostly represented by law magazines, lectures, judicial practice and legislation and jurisprudence websites. All of them being listed in the bibliography.