The article discusses the features of attributing a business entity to a small business entity. The dynamics of the development of small business in Russia, in the Volga federal district and in the Republic of Mordovia for 2013-2017 is investigated. Studied one of the factors affecting the development of small business in Russia - taxation. The current regimes of calculation and collection of taxes on small businesses in the Russian Federation and their changes in 2018, and the features of the organization of accounting, with a particular tax system are considered. The dynamics of the number of enterprises using the simplified taxation system is given.