The authority for discretionary spending stems from annual appropriation acts, which are under the control of the House and Senate Appropriations Committees. Most defense, education, and transportation programs, for example, are funded that way, as are a variety of other federal programs and activities. Those appropriations are subject to a set of budget enforcement rules and processes that differ from those that apply to mandatory spending. As the Congress considers appropriation acts, CBO tallies the budget authority those acts would provide and estimates the outlays that would result.
Mandatory—or direct—spending includes spending for entitlement programs and certain other payments to people, businesses, and state and local governments. Mandatory spending is generally governed by statutory criteria; it is not normally set by annual appropriation acts. Outlays for the nation’s three largest entitlement programs (Social Security, Medicare, and Medicaid) and for many smaller programs (unemployment compensation, retirement programs for federal employees, student loans, and deposit insurance, for example) are mandatory spending. Social Security and some other mandatory spending programs are in effect indefinitely, but some (for example, some agriculture programs) expire at the end of a given period. Roughly 60 percent of federal spending in 2012 (other than for the government’s net interest costs) was mandatory. Legislation that changed direct spending would, by itself, affect the budget deficit because no further legislative action would be required for the change in spending to occur.