We consider the relationship between legality principle and parties’ equality principle in the claim proceed-ings. We believe that the basis for ensuring the actual implementation of this principle is a correct understanding of the interdependence of these principles. We focus special attention on the interdependence of legality and equality of the parties, which in absolute terms can be regarded as a sign of complementarity. We aim to analyze the relationship between legality principle and parties’ equality principle in the claim proceedings. Tasks: to study the concept and significance of the principle of “legality” and “equality”, to consider the problems of implementing these principles of the Code of Civil Procedure of the Russian Federation, to propose improvements for the process of implementing these principles in the Code of Civil Procedure of the Russian Federation. We establish that the reason for non-compliance with certain requirements, leading to the abandonment of the statement of claim, may be the unfair (un) intentional activities of some interested parties. Our contribution to the study is to identify a procedural defect in Article 147 of the Code of Civil Procedure of the Russian Federation. This article does not directly contain a prohibition for the court at the stage of preparation for the court session, to hold a court session without proper notification of the parties, which is a violation of the principles of legality and equality of the parties in the proceedings. On this basis, we consider it possible to correct and (or) supplement Article 147 of the Code of Civil Procedure of the Russian Federation with part 3. The need for these changes is justified by the importance of ensuring real equality of parties.