The work is devoted to the study of the use of business models of financial outsourcing in the institutional support of sustainable development. It is shown that a significant role in the sustainable development of the economy and environmental management can belong to clients of financial outsourcing services - small and medium-sized businesses (SMEs). The paper proposes to include an outsourcing company of financial outsourcing services in the infrastructure for supporting sustainable economic development of united territorial communities (UTC), which will increase the volume of revenues to the local budget and provide additional financing for SMEs, incl. whose activities are aimed at improving the environmental situation. A methodology for monitoring the revenue side of local budgets has been developed by processing monthly data “Openbudget” and “Opendata” by methods of predictive analytics. The proposed methodology has been tested on the example of the budget of Mariupol (Ukraine), as a city with a poor environmental situation, in which monitoring of the local budget will reveal additional sources of financing for the activities of SMEs - clients of financial outsourcing services aimed at improving the environment, as well as ensuring sustainable development of the economy of the territories and the country.