Where Does Federal Income Tax Go: Social Security, Defense, Debt

Federal income tax goes into the General Fund of the U.S. Treasury, the government’s main checking account, and Congress and the President decide each year how to spend it through the federal budget.¹ The largest shares pay for Social Security (about 22 percent of spending), health care programs including Medicare and Medicaid (roughly 30 percent combined), national defense (14 percent), and interest on the federal debt (14 percent).² The rest covers veterans’ benefits, safety-net programs, transportation, scientific research, and the operating costs of the government itself. Individual income taxes are the single biggest source of federal revenue, providing about 52 percent of the total in fiscal year 2026.³

From Your Paycheck to the Budget

When your employer withholds federal income tax, or when you send a quarterly estimated payment, the money lands in the General Fund alongside corporate income taxes, excise taxes, and other receipts.¹ From there, the dollars aren’t earmarked for any specific program. Congress directs them through two very different kinds of spending.

Mandatory spending is locked in by existing laws. If you meet the eligibility rules for Social Security, Medicare, or Medicaid, the government pays. Congress doesn’t vote each year on whether to fund these programs. Discretionary spending is the opposite: Congress sets the funding level for defense, transportation, science, courts, and most other agencies through annual appropriations bills. In fiscal year 2026, mandatory programs account for about 60 percent of federal outlays, discretionary programs roughly 26 percent, and interest on the debt the remaining 14 percent. Total federal spending in fiscal year 2026 is projected at $7.4 trillion.⁴

The Full Spending Breakdown

Based on Treasury data for fiscal year 2026, federal spending divides roughly like this:²

Social Security: 22 percent
Medicare: 16 percent
Net interest on the debt: 14 percent
National defense: 14 percent
Health, including Medicaid: 14 percent
Income security and safety-net programs: 9 percent
Veterans’ benefits and services: 6 percent
Education, training, and employment: 2 percent
Transportation: 2 percent
All other, including courts, diplomacy, and science: about 1 percent

Social Security

Social Security is the single largest line in the federal budget, with projected outlays of roughly $1.7 trillion in fiscal year 2026.⁵ The program pays retirement benefits to older Americans, disability payments to workers who can no longer hold a job, and survivor benefits to families of deceased workers. It is funded mostly by dedicated FICA payroll taxes rather than income tax, with some general revenue support.⁶ For 2026, beneficiaries received a 2.8 percent cost-of-living adjustment.⁷

Medicare and Medicaid

Federal health spending splits between Medicare and a broader health category that includes Medicaid. Together they take about 30 percent of the budget, with the Congressional Budget Office projecting combined costs of roughly $1.9 trillion in fiscal year 2026.⁴

Medicare provides health insurance mainly for people 65 and older. Hospital coverage is largely funded through payroll taxes, while doctor visits, outpatient care, and prescription drugs are funded through a mix of beneficiary premiums and general revenue.⁸ Medicaid is a joint federal-state program covering low-income individuals, children, pregnant women, seniors, and people with disabilities. States run their own programs within federal minimum standards, and coverage varies by state.⁹ Medicaid covered an estimated 109 million people in recent years.¹⁰ Both are entitlements, so the government pays for every eligible person who enrolls.

National Defense

National defense makes up about 14 percent of federal spending. The President’s fiscal year 2026 budget requested roughly $1.3 trillion for total defense, including the Department of Defense and defense-related work at other agencies.¹¹ The money pays for service members’ salaries and health care, weapons procurement, research and development, cybersecurity, maintenance of the nuclear arsenal, and the day-to-day operation of bases and equipment worldwide. Because defense is discretionary, Congress sets the level each year, and it remains by far the largest piece of the discretionary budget.

Interest on the Federal Debt

Interest payments now rival defense in size. The CBO projects net interest at $1.03 trillion in fiscal year 2026, about 3.3 percent of GDP, above the 50-year average of 2.1 percent.⁴ The total national debt sits at approximately $38.8 trillion in early 2026.¹²

When federal spending exceeds revenue, the Treasury borrows the difference by selling bonds, bills, and notes.¹³ Paying interest on those securities is a legal obligation, and unlike the rest of the budget, that money doesn’t fund any program or service. It’s the carrying cost of past borrowing.

Veterans’ Benefits

About 6 percent of federal spending goes to the Department of Veterans Affairs, which requested $441.3 billion for fiscal year 2026.¹⁴ The VA delivers health care through a nationwide hospital and clinic network, pays disability compensation and pensions, funds GI Bill education benefits, and provides housing assistance. Disability compensation and pensions are mandatory, while VA health care and construction funding are set by Congress each year.

Income Security and Safety-Net Programs

About 9 percent of the budget goes to programs that help people facing financial hardship. Most are means-tested: you qualify based on income below a set threshold.

The Supplemental Nutrition Assistance Program (SNAP) helps low-income households buy food, with projected spending of about $100 billion in fiscal year 2026. Refundable tax credits, including the Earned Income Tax Credit, are projected at roughly $105 billion.⁴ The EITC pays money back to low- and moderate-income workers even if they owe no income tax, particularly those with children.¹⁵ Federal housing assistance is another major piece: the Housing Choice Voucher Program provides rental subsidies to over 2.3 million families.¹⁶ Unemployment insurance, Supplemental Security Income for aged and disabled individuals with limited resources, and Temporary Assistance for Needy Families also fall in this category.

Transportation, Science, and Running the Government

The remaining slices keep the country’s physical and institutional infrastructure running. Transportation is about 2 percent of spending; the Federal Highway Administration alone requested $72.6 billion for fiscal year 2026 to design, build, and maintain highways and bridges.¹⁷

Federal research funding covers agencies like NASA, with an $18.8 billion request for space exploration, earth science, and aeronautics,¹⁸ and the National Institutes of Health, at a requested program level of $27.9 billion.¹⁹ Tax dollars also pay to run the government itself. The federal judiciary requested about $10.3 billion for fiscal year 2026 to operate courts across the country,²⁰ and agencies like the National Weather Service and the Federal Aviation Administration rely on annual appropriations to deliver forecasts and run air traffic control.

Spending Through the Tax Code

Not every federal “spending” decision shows up as a check going out. The tax code itself contains deductions, credits, and exclusions that reduce what people owe, and the Treasury projects these tax expenditures at $2.3 trillion in fiscal year 2026, a figure that rivals total discretionary spending. The largest are the exclusion of employer-provided health insurance (about $309 billion), the exclusion of net imputed rental income for homeowners (about $185 billion), and tax deferral on defined contribution retirement plans like 401(k)s (about $181 billion).²¹ A $100 tax break and a $100 grant have the same effect on the deficit, so these provisions shape where your income tax effectively goes even though no program spends the money directly.

What’s Coming for the Biggest Programs

Two of the largest categories face known funding pressure. The Social Security retirement trust fund is projected to be depleted by 2033, and the combined retirement and disability trust funds by 2034. Medicare’s Hospital Insurance trust fund faces the same 2033 deadline. Depletion doesn’t end these programs. It means incoming payroll taxes would only cover a portion of scheduled benefits, which for Social Security would likely trigger an automatic reduction of roughly 17 to 21 percent unless Congress acts. Medicare Part B and Part D draw on premiums and general revenue that adjust automatically, so those portions are considered solvent indefinitely.²²

Interest on the debt is the fastest-growing piece of the budget. The CBO projects net interest will climb from $1.03 trillion in 2026 to $2.1 trillion by 2036, taking a larger share of tax revenue each year and leaving less room for everything else.⁴

1
U.S. Department of the Treasury. Accounting and Budget FAQs
2
U.S. Treasury Fiscal Data. Federal Spending
3
U.S. Treasury Fiscal Data. Government Revenue
4
Congressional Budget Office. The Budget and Economic Outlook: 2026 to 2036
5
Social Security Administration. FY 2026 Justification of Estimates for Appropriations Committees
6
Cornell Law School. Payroll Taxes
7
Social Security Administration. 2026 Cost-of-Living Adjustment (COLA) Fact Sheet
8
Medicare.gov. Get Started With Medicare
9
HHS.gov. What’s the Difference Between Medicare and Medicaid
10
MACPAC. Medicaid 101
11
The White House. Department of Defense Appendix – Technical Supplement to the 2026 Budget
12
U.S. Treasury Fiscal Data. U.S. Treasury Fiscal Data
13
U.S. Treasury Fiscal Data. National Deficit
14
U.S. Department of Veterans Affairs. 2026 Budget Highlights
15
Internal Revenue Service. Earned Income Tax Credit (EITC)
16
U.S. Department of Housing and Urban Development. Housing Choice Voucher Program
17
U.S. Department of Transportation. FHWA FY 2026 Budget Estimates
18
National Aeronautics and Space Administration. FY 2026 President’s Budget Request Summary
19
National Institutes of Health. Office of Budget
20
U.S. Courts. The Judiciary Fiscal Year 2026 Congressional Budget Summary
21
U.S. Department of the Treasury. Tax Expenditures Fiscal Year 2026
22
Social Security Administration. A Summary of the 2025 Annual Reports