Limits Annual Choices
Because mandatory programs and interest payments consume most of the budget, the share lawmakers actively debate each year is relatively small.
In plain English
Some federal spending runs on autopilot under existing law, while other spending has to be voted on by Congress every year.
Simple example
In fiscal year 2023, mandatory programs and net interest accounted for roughly three-quarters of federal spending, while discretionary spending — including defense and most domestic agencies — made up the remainder, according to the Congressional Budget Office.
Why it matters
What the term actually changes.
Shapes Reform Debates
Changing mandatory spending generally requires altering the underlying laws, making programs like Social Security and Medicare politically harder to adjust than annual agency budgets.
How it works
The mechanics, in practice.
Mandatory Programs
Spending levels are determined by eligibility rules written into law, so costs rise or fall with the number of people who qualify rather than yearly votes.
Discretionary Appropriations
Congress passes appropriations bills each fiscal year setting funding amounts for agencies and programs, from the military to national parks.
Interest On Debt
The Treasury must pay interest on outstanding federal debt, an amount that shifts with interest rates and the size of the debt.