Abstract: The subject of the research is the tax expenditures defined as the fallout out of the budget system as a result of granted tax rebates, preferences and other tax regime reliefs. The article is devoted to the principles of referring tax rebates to tax expenditures as well as the development of methodological approaches to reviewing tax legislation in order to define criteria tax rebate criteria and develop the methodological basis for evaluation of the shortfall in the budget by keeping the register of tax expenditures based on the principles of budget classification. The methodology of the research is based on the principles of systems analysis, synthesis, comparison, generalisation that allow to define approaches to classification of tax expenditures. The authors offer their own principles for developing the tax expenditure register and tax rebate register. These principles include neutrality, justice, efficiency, approximation and legitimacy. The novelty of the research is caused by the fact that the authors develop criteria for selection of tax preferences, rebates and other tax regiem reliefs to include them into the register of tax expenditures. The practical importance of the research is that the authors offer the register of tax expenditures based on the principles of existing budget classification adn taking into account the designated use of each kind in particular. The development of such register will raise efficiency of mnaging the resources of the Russian Federation budgetary system and to create conditions for elimination of negative effects caused by the inter-country competition for the taxation base.