The issues of timber logging are not only of natural, but also of legal nature. A complicated procedure related to the certification of wood is required to ensure that wood can be subject to a course of trade. Wood trade is regulated by the national law. However, it is also delimited in the European Union legislation, which is extremely important in the context of Poland’s EU membership. The legality of the origin of timber is confirmed by its marking. That process also aims at ensuring lawfulness of a timber trade and preventing illegal logging. The purpose of this article is to present the legal aspects of wood marking and the responsibility of the entity that harvested it. The manuscript contains also an analysis of legal regulations related to procedures allowing the entry of timber into legal transactions. Due to the fact that the legal acquisition of a timber is always based on formalized files (forest management plans) or an administrative decision, the only possible research method we could adopt is the dogmatic and legal method. Our findings concern forests belonging to the State Treasury and other entities located throughout Poland. We analysed binding regulations, case law and literature and determined which procedures should be implemented to talk about legal logging. The main problems concern entities other than the State Treasury. We pointed out the consequences of the illegal introduction of a timber into legal transactions. We also clarified the doubts arising in relation to the certificate of legality of the harvested timber as a document confirming its origin. The certificate should be included in the acts of administration, and therefore, similarly to the case of a timber marking, public administration activities subject to the control of administrative courts. An important element of the study are also the arrangements made in the field of administrative fines related to illegal activities towards forests, which constitute the state budget income.