Your paycheck has federal income tax, Social Security tax, and Medicare tax removed before you see it

The amount taken out depends on three things: how much you earn, what you claim on your W-4 form, and your state. Federal income tax is withheld based on tax brackets and the number of dependents you report. Social Security tax is a flat 6.2% of your gross pay (up to an annual cap). Medicare tax is 2.9% of everything you earn, with an additional 0.9% if you make over $200,000 as a single filer or $250,000 if married filing jointly. Some states also take state income tax, and a few cities add local tax on top.

Your employer sends these withheld amounts to the IRS and your state revenue department throughout the year. At tax time, the IRS compares what was withheld to what you actually owe. If too much was taken, you get a refund. If too little was taken, you owe the difference.

Key Takeaways

  • Federal income tax withholding is based on your W-4 form, which you fill out when hired or can change anytime by submitting a new one to your employer.
  • Social Security and Medicare taxes are fixed percentages (6.2% and 2.9%) that come out of every paycheck regardless of your W-4 choices.
  • The amount of federal income tax withheld changes if you claim more dependents, have a second job, or earn investment income.
  • Your actual tax bill at the end of the year may be higher or lower than what was withheld, which is why you may owe money or receive a refund.

How federal income tax withholding works

Your employer uses your W-4 form to calculate how much federal income tax to remove from each paycheck. The W-4 asks for your filing status (single, married, head of household), the number of dependents you claim, and any other income or deductions. The more dependents you claim, the less federal tax is withheld. The fewer dependents you claim, the more is withheld.

The IRS publishes tax tables and a withholding calculator every year. Your employer's payroll system plugs your W-4 information into these tables to figure out the exact amount. If you claim zero dependents, more money comes out. If you claim five dependents, less comes out. You can change your W-4 anytime by giving your employer a new form — you do not have to wait until next year.

Federal income tax is progressive, meaning higher earners pay a higher percentage. In 2024, federal tax brackets range from 10% to 37%, but these are marginal rates — only the income in each bracket is taxed at that rate. Your paycheck withholding is spread across the year, so each check reflects a portion of your annual tax burden.

Social Security and Medicare taxes are separate from income tax

Social Security tax and Medicare tax are payroll taxes, not income taxes. They come out of every paycheck at fixed rates and go to specific government programs. Social Security tax is 6.2% of your gross pay, up to a maximum of $168,600 in annual earnings for 2024 (this cap changes yearly). Once you hit that cap, no more Social Security tax is withheld for the rest of the year. Medicare tax is 2.9% of all your earnings with no cap.

If you earn over $200,000 as a single filer or $250,000 if married filing jointly, an additional 0.9% Medicare tax is withheld. This extra tax has no cap and continues for the rest of your life, even after you retire. Unlike federal income tax, you cannot change how much Social Security and Medicare tax is withheld — the rate is the same for everyone.

Your employer also pays an equal amount of Social Security and Medicare tax on your behalf (6.2% and 2.9%), but this does not appear on your paycheck. These employer contributions go directly to the government.

State and local income taxes vary by where you live and work

Forty-one states have a state income tax, and a handful of cities add local income tax on top. The rates and rules differ widely. Some states use a flat tax rate (the same percentage for everyone), while others use progressive brackets like the federal system. A few states have no income tax at all — Alaska, Florida, Nevada, South Dakota, Tennessee, Texas, Washington, and Wyoming.

Your employer withholds state and local tax based on where you work, not where you live. If you work in a state with income tax but live in a state without it, state tax is still withheld from your paycheck. At tax time, you may get a credit or refund for taxes paid to the wrong state. If you work in multiple states during the year, your withholding becomes more complex, and you may owe or be owed money when you file.

Some states allow you to claim dependents or deductions on a state W-4 form, similar to the federal form. Others do not. Check your state's revenue department website to see if you can adjust your state withholding.

Why your withholding might not match what you actually owe

Withholding is an estimate. Your employer calculates it based on the assumption that you will earn the same amount every pay period for the entire year. If your income changes, your withholding will not automatically adjust. If you get a raise, a bonus, or a second job, you may not have enough withheld. If you lose a job or take unpaid leave, you may have too much withheld.

Other things that affect your actual tax bill but not your withholding include deductions (mortgage interest, charitable donations, student loan interest), tax credits (child tax credit, earned income tax credit), investment income, and self-employment income. Your W-4 has a section for "other income," but many people do not fill it out. If you have significant income outside your job, you should adjust your W-4 or make estimated tax payments to avoid owing a large amount at tax time.

The IRS withholding calculator on IRS.gov can help you figure out if your withholding is correct. You can use it anytime during the year, and if it shows you will owe or get a large refund, you can submit a new W-4 to your employer to adjust your withholding.

How to read your pay stub

Your pay stub shows gross pay (before deductions), then lists each deduction separately. Federal income tax withholding appears as "FIT" or "Federal Income Tax." Social Security appears as "FICA-Social Security" or "OASDI." Medicare appears as "FICA-Medicare" or "HI" (Hospital Insurance). State and local taxes appear with their state or city abbreviation.

Below the deductions, you will see your net pay or "take-home pay" — the amount actually deposited into your account. Your pay stub also shows year-to-date totals for each deduction, so you can track how much has been withheld so far this year. If you notice a sudden change in withholding, check whether you submitted a new W-4 or whether your employer made an error. Contact your payroll department if something looks wrong.

Some pay stubs also show pre-tax deductions like health insurance premiums, 401(k) contributions, or dependent care accounts. These reduce your taxable income, which lowers your federal and state income tax withholding. Post-tax deductions like life insurance or union dues come out after taxes are calculated.

What to do if too much or too little is being withheld

If you consistently get a large refund, too much is being withheld. You can claim more dependents on your W-4 to reduce withholding and take home more money each paycheck. If you consistently owe money at tax time, too little is being withheld. You can claim fewer dependents or check the "extra withholding" box on your W-4 to have additional money removed from each check.

Fill out a new W-4 form and give it to your payroll or human resources department. The change takes effect on your next paycheck. You can submit a new W-4 as many times as you need during the year. If you have a major life change — marriage, divorce, a child, a new job, or a significant income change — update your W-4 within a few weeks so your withholding stays accurate.

If you are self-employed or have income that is not subject to withholding, you may need to make quarterly estimated tax payments instead of relying on employer withholding. The IRS sends notices for these payments in January, April, June, and September. Talk to a tax professional if you are unsure whether you need to make estimated payments.

Frequently Asked Questions

Can I claim zero dependents to get a bigger paycheck?

Yes, but this means more federal income tax is withheld, so your take-home pay will be smaller. You might do this if you want to ensure you do not owe money at tax time, or if you have income not subject to withholding. At tax time, you will likely get a refund, but that refund is your own money returned to you — it is not extra money.

Why do I owe taxes if my employer already withheld federal tax?

Withholding is based on your W-4, which is an estimate. If you have a second job, investment income, or claimed too many dependents, your withholding may not cover your actual tax bill. You can adjust your W-4 mid-year to increase withholding, or you can pay the amount owed when you file your tax return.

Does my employer's contribution to Social Security and Medicare affect my paycheck?

No. Your employer pays an equal amount (6.2% Social Security, 2.9% Medicare) directly to the government on your behalf. This does not reduce your paycheck. However, you are responsible for the employee portion (6.2% and 2.9%), which is withheld from your gross pay before you receive it.

What happens to the money withheld from my paycheck?

Federal income tax goes to the U.S. Treasury. Social Security tax funds the Social Security program for retirees, disabled workers, and survivors. Medicare tax funds the Medicare program for people 65 and older and some younger people with disabilities. State and local taxes fund state and local government services. Your employer sends these amounts to the appropriate agencies throughout the year.

Can I change my withholding if I get married or have a child?

Yes. Marriage and children change your filing status and dependent count, which affects your withholding. Submit a new W-4 to your employer within a few weeks of the change. You can also use the IRS withholding calculator to see if your current withholding is still correct.