Spending programs and tax expenditures are the two primary ways that the federal government provides benefits to the public. Each type of intervention represents a transfer from the government to individuals and firms, though differences in the budget process, saliency, and targeting may have ramifications for usage across different types of services. Federal expenditures (spending) are transfers from the federal government to individuals, firms, or institutions that do not draw directly from individual or corporate tax liability. Federal spending programs fall into three broad categories: (1) discretionary spending, (2) mandatory spending, and (3) net interest payments. The Congressional Budget Office (CBO) estimates that federal resources devoted to spending programs will total $4.407 trillion in FY2019, or 20.7% of annual gross domestic product (GDP). Tax expenditures are revenue losses attributable to federal tax provisions. There are three main types of tax expenditures: (1) exclusions, exemptions, and deductions from gross personal or corporate income; (2) preferential tax rates for certain programs; and (3) refundable and nonrefundable tax credits. The Joint Committee on Taxation (JCT) estimates the revenue losses attributable to certain programs. As of October 2018, projected revenue losses due to tax expenditures in FY2017 summed to $1.485 trillion, or 7.0% of GDP. Holding other activities constant, an increase in spending programs or tax expenditures each increases net budget deficits. The characteristics and composition of spending and tax expenditures may have distinct implications for the way each is used across major sectors of the federal budget. Federal spending programs may more efficiently target groups that are unlikely to file federal tax returns, like low-income and elderly households. Tax expenditures may be more likely than spending programs to utilize targeting and enforcement services already undertaken by the federal government. Discretionary spending and, in some cases, expiring tax expenditures typically involve more frequent legislative action than mandatory spending and permanent tax expenditure programs. Discretionary spending programs also provide increased budget certainty to Congress through the use of budget authority, while mandatory spending and tax expenditure resources depend on the participation and benefit choices of program recipients. This report identifies the largest spending and tax expenditures across eight major categories of federal activity: (1) defense and international affairs; (2) general science, space and technology, natural resources and the environment, and agriculture; (3) commerce and housing, community and regional development, and transportation; (4) education, training, employment, and social services; (5) health, including Medicare; (6) income security; (7) Social Security and veterans' benefits; and (8) administration of justice and general governance. [ABSTRACT FROM AUTHOR]