The pieces of payroll tax withheld from your paycheck

Payroll tax is not one tax — it is three separate taxes taken from your paycheck, plus a matching amount your employer pays on your behalf. The three are Social Security tax, Medicare tax, and federal income tax withholding. Each one funds a different program, uses a different rate, and has different rules about how much you owe.

When you see your pay stub, the line items show these three separately. Social Security and Medicare together are often called FICA taxes (Federal Insurance Contributions Act). Federal income tax withholding is separate and is calculated differently — it depends on your filing status, the number of dependents you claim, and your total income for the year.

Some states and cities also take income tax from your paycheck, but those are not part of federal payroll tax. This article covers only the federal taxes that appear on every pay stub.

Key Takeaways

  • Social Security tax is 6.2 percent of your wages up to a yearly cap, which your employer matches.
  • Medicare tax is 1.45 percent of all your wages with no cap, and your employer matches that amount too.
  • Federal income tax withholding is calculated based on your W-4 form and varies by person — it is not a fixed percentage.
  • Self-employed people pay both the employee and employer portions of Social Security and Medicare tax, totaling 15.3 percent.
  • Your employer sends all three taxes to the IRS on your behalf, and the amounts withheld reduce what you owe when you file your return.

Social Security tax: 6.2 percent up to the wage base

Social Security tax funds the Social Security program, which pays retirement benefits, disability benefits, and survivor benefits. The rate is 6.2 percent of your wages, and your employer pays an equal 6.2 percent. Together, that is 12.4 percent of your pay going to Social Security.

The catch is the wage base limit. In 2024, you pay Social Security tax only on the first $168,600 of income you earn in a year. Once you reach that amount, no more Social Security tax is withheld from the rest of your paychecks that year. Your employer also stops matching at that point. The wage base limit changes each year — it is adjusted based on average wage growth in the economy.

This means high earners pay a smaller percentage of their total income in Social Security tax than lower earners do. Someone earning $50,000 pays 6.2 percent on all of it. Someone earning $500,000 pays 6.2 percent only on the first $168,600, which is about 2 percent of their total income.

Medicare tax: 1.45 percent with no wage cap

Medicare tax funds the Medicare program, which provides health insurance to people 65 and older and some younger people with disabilities. The rate is 1.45 percent of your wages, and your employer matches it. There is no wage base limit — you pay Medicare tax on every dollar you earn, no matter how much you make.

High earners pay an additional Medicare tax of 0.9 percent on wages above a threshold. For 2024, that threshold is $200,000 for single filers, $250,000 for married filing jointly, and $125,000 for married filing separately. This additional tax is withheld from your paycheck if you cross the threshold, and you do not get an employer match on it — you pay the full 0.9 percent yourself.

Unlike Social Security tax, which stops at the wage base, Medicare tax continues on every paycheck throughout the year. This is why your Medicare withholding is often the same amount on each check, while your Social Security withholding may drop to zero partway through the year if you are a high earner.

Federal income tax withholding: based on your W-4

Federal income tax withholding is the third piece of payroll tax. Unlike Social Security and Medicare, which use a fixed percentage, federal withholding is calculated based on information you provide on your W-4 form (Employee's Withholding Certificate). Your employer uses your W-4 to estimate how much federal income tax you will owe for the year, then withholds that amount spread across your paychecks.

The W-4 asks for your filing status (single, married, head of household), the number of dependents you claim, and any other income or adjustments. The more dependents you claim or the more adjustments you make, the less your employer withholds. The less you claim, the more is withheld. You can change your W-4 at any time during the year if your situation changes — for example, if you get married, have a child, or take a second job.

Federal withholding is not a fixed tax rate. It is an estimate. If too much is withheld, you get a refund when you file your tax return. If too little is withheld, you owe money. The goal of the W-4 is to get the estimate as close as possible so you do not have a large refund or a large bill at tax time.

How self-employed people pay payroll tax

If you are self-employed, you pay both the employee and employer portions of Social Security and Medicare tax yourself. This is called self-employment tax. The total rate is 15.3 percent: 12.4 percent for Social Security (up to the wage base) and 2.9 percent for Medicare (1.45 percent times two).

Self-employed people calculate self-employment tax on Schedule SE (Self-Employment Tax) and pay it along with their federal income tax. You can deduct half of your self-employment tax when you calculate your adjusted gross income, which reduces your taxable income slightly. You also pay federal income tax withholding, but you do this by making quarterly estimated tax payments to the IRS instead of having it withheld from a paycheck.

Where your payroll tax goes

Your employer sends all three taxes to the IRS on your behalf. The IRS then distributes the money to the programs they fund. Social Security tax goes to the Social Security Trust Fund. Medicare tax goes to the Medicare Trust Fund. Federal income tax withholding goes to the general Treasury to fund federal government operations.

When you file your tax return, the amount of federal income tax withheld during the year is credited against what you owe. If you withheld more than you owe, you get a refund. If you withheld less, you pay the difference. Social Security and Medicare taxes are not refundable — they are not credits against your income tax bill. They are separate taxes that fund separate programs.

How payroll tax appears on your pay stub

Your pay stub breaks down each tax separately so you can see exactly how much was withheld. You will see a line for Social Security (often labeled "OASDI" for Old-Age, Survivors, and Disability Insurance), a line for Medicare, and a line for federal income tax withholding. Some pay stubs also show state and local income tax if you live in a state or city that has income tax.

The pay stub also shows your employer's matching contributions for Social Security and Medicare, though this amount does not come out of your paycheck — it is paid by your employer. Knowing what each line represents helps you understand where your money goes and whether the withholding is correct for your situation.

Frequently Asked Questions

Why do I pay Social Security tax if I might not collect it?

Social Security tax funds not just retirement benefits but also disability and survivor benefits. Even if you never retire, you or your family may receive benefits if you become disabled or if you die and have dependents. The tax is mandatory for all workers because the program is designed to protect everyone, not just retirees.

Can I opt out of paying payroll tax?

No. Payroll tax is mandatory for all employees and self-employed people. The only exceptions are certain religious groups that have been granted exemptions by the IRS, and some government employees hired before specific dates who are covered by different pension systems instead.

What happens to the money I pay in payroll tax?

Social Security and Medicare taxes go into trust funds that pay current beneficiaries. Federal income tax withholding goes to the general Treasury. You do not have a personal account — the taxes you pay now fund benefits for people receiving them today. When you retire or become may be able to access for Medicare, your benefits come from taxes paid by workers at that time.

Why is my Social Security withholding different on each paycheck?

If you are a high earner, your Social Security withholding stops once you reach the yearly wage base limit. Early in the year, you pay 6.2 percent on each check. Once you hit the limit, that line goes to zero for the rest of the year. If you have multiple jobs, you may overpay Social Security tax across all jobs, but you can claim a credit on your tax return.

Is federal income tax withholding the same as my actual tax bill?

No. Federal withholding is an estimate based on your W-4. Your actual tax bill depends on your total income, deductions, and credits for the year. If you withheld too much, you get a refund. If you withheld too little, you owe the difference when you file your return.