This article examines the scientific issues surrounding the codification of civil and civil procedural legislation. The aim of the study is to substantiate the most comprehensive codification of civil and civil procedural legislation and harmonize them. It is noted that the proposed separate codification of business legislation by removing provisions regulating business relations from the Civil Code of the Russian Federation would violate the principle of unity of civil-law regulation of private relations enshrined in the Civil Code of the Russian Federation, which is unacceptable. The article also substantiates the need to adopt a unified Code of Civil Procedure of the Russian Federation that would include procedural rules governing arbitration proceedings, which are, by their nature, norms of civil procedural law. Achieving this goal would contribute to the enshrinement of the principle of unity of legal regulation of proceedings in cases arising from private relations in the Code of Civil Procedure of the Russian Federation. This approach would align the codification of civil legislation governing private relations with the codification of civil procedural legislation governing procedural relations in resolving disputes arising from private relations.