Often called “entitlement spending” or “auto-pilot spending,” mandatory spending goes on automatically from year to year and is not decided by the regular appropriations process. Mandatory spending is the only type of spending, other than interest on the debt, that’s exempt from regular appropriations.
The largest entitlement programs are Social Security, Medicare, and Medicaid. Mandatory spending cost $2.4 trillion in 2016–that is over 60 percent of federal spending overall.
These programs are typically created when lawmakers set a particular program’s requirements and parameters (at what age or income level is a person eligible for Social Security? At what income level does someone qualify for Medicaid?) and then the spending goes on regularly regardless of what Congress passes in the budget. Of course, for the last several decades, most spending is authorized in continuing resolutions and other types of temporary spending bills, making reforming these programs even more difficult.