Topicality. Tax instruments that are aimed on stimulation of economic activity are widely used as regulators of regional territorial economic systems in developed countries, especially in the EU, and for Ukraine this practice, on the author's opinion and on the opinion of many experts in taxation sphere, will also support economic development priorities and would be appropriate and effective. The processes of voluntary formation of united territorial communities and decentralization of administrative-territorial organization in Ukraine did not bring the expected growth in the economic development of territorial economic systems and this necessitates the formation of a comprehensive policy to promote economic development of territorial complexes with special emphasis on economic growth. Supporting the priorities of economic development of regional, subregional economic systems and parts of functional areas at the basic level can be effectively implemented through tax instruments, because such measures are effective and can stimulate the rapid direction of financial, commodity, logistics, investment flows towards favorable business conditions. A promising direction for the development of territorial economic systems is the support of economic cooperation in communities, because this will provide conditions for the division of labor in the territorial dimension and will stimulate the creation of extended value chains.Aim and tasks. The purpose of the article is to substantiate the feasibility and determine the potential effectiveness of tax instruments that are to stimulate the economic development and cooperation of territorial communities in Ukraine in the context of administrative and territorial reform and according to the impact of modern challenges of the ensuring of the competitiveness of domestic economic complexes in context of integration into world economic systems.Research results. The article considers the tools of economic cooperation of communities as means of functional territories creating, which is an alternative to the process of united territorial communities forming, and as a universal mean of ensuring of the economic capacity of communities in terms of unification, which is especially relevant during the completing of decentralization reform, when delegation of all powers is provided to the Cabinet of Ministers of Ukraine.Measures of economic capacity increase of territorial communities with the use of economic cooperation tools are developed in the article, including tax, organizational, financial, informational levers that are relevant to the current conditions of development of territorial communities in Ukraine and regions. Particular attention is paid to tax measures and mechanisms that are to stimulate economic development and cooperation of local communities, as it is proved that such levers of regulation are among the most effective.Conclusion. It is determined that stimulation of investment activity, general economic development and cooperation by tax regulation measures is already possible and appropriate institutional support for such tools has already been formed, but for further introduction of a comprehensive mechanism of tax stimulation of cooperation and formation of functional territories on the basis of effective division of labor support, additional more significant and systemic changes to the current institutional environment, especially to the Tax Code of Ukraine are needed.