At present, in the era of globalization of the world economy, a significant place is given to the process of harmonization of tax legislation within the framework of various integration associations. The harmonization of tax legislation not only contributes to the proper functioning of the internal market but can also be considered in a broader sense as a tool for the proper functioning of national tax systems, helping to eliminate tax obstacles at the international level, unfair taxation competition, the fight against violations of tax laws, and the solution to many social, economic and political problems both within the country and at the level of the relevant integration associations. Considering the importance of the process of harmonization of tax legislation in the EAEU member states, it becomes obvious that it is necessary to study the experience of other integration associations, including the EU. The paper substantiates the need to harmonize the tax legislation of the EAEU member states, reform national tax systems to bring the levels of economic development of the EAEU member states closer together, and use legal mechanisms that help remove barriers and obstacles to building a single internal market for goods, works, services.