What gets taken out of your paycheck and why

Your employer withholds four separate taxes from each paycheck: Social Security, Medicare, federal income tax, and (in most states) state income tax. Social Security and Medicare are FICA taxes, named after the Federal Insurance Contributions Act. Your employer also pays matching amounts for Social Security and Medicare on your behalf — money that does not appear on your stub but counts toward your benefits. Federal income tax and state income tax are withheld based on the W-4 form you filled out when you started the job.

The amount withheld is not a penalty or a loan. It is a prepayment of taxes you will owe at the end of the year. When you file your tax return in April, 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.

The withholding system exists because the federal government collects taxes throughout the year rather than waiting until April. Without it, most workers would owe a large lump sum they could not pay.

Key Takeaways

  • Social Security tax is 6.2% of your wages up to a yearly cap (the cap changes each year), and Medicare tax is 1.45% of all wages with no cap.
  • Federal income tax withholding depends on your W-4 form, which tells your employer how many dependents you claim and whether you have other income.
  • Your employer matches your Social Security and Medicare contributions, but this matching amount does not appear on your paycheck.
  • State income tax withholding varies by state — some states have no income tax, while others withhold a percentage similar to federal tax.
  • The total withheld is an estimate; your actual tax bill is calculated when you file your return, and you may receive a refund or owe more.

How Social Security and Medicare withholding work

Social Security tax is 6.2% of your gross wages, but only up to a yearly earnings cap. In 2024, that cap is $168,600 — meaning once you earn that much in a calendar year, no more Social Security tax is withheld from your remaining paychecks. The cap changes each year based on wage growth. Medicare tax is 1.45% of all your wages with no earnings cap, so it continues to be withheld no matter how much you earn.

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 on the amount above that threshold. This is called the Net Investment Income Tax and applies to both wages and investment income.

Your employer withholds these amounts and sends them to the IRS on your behalf. At the same time, your employer pays an equal amount (6.2% for Social Security, 1.45% for Medicare) as their own contribution. Self-employed people pay both the employee and employer portions, totaling 15.3% for Social Security and Medicare combined.

How federal income tax withholding is calculated

Federal income tax withholding is based on the W-4 form you complete when you start a job. The W-4 asks for your filing status (single, married, head of household), the number of dependents you claim, and whether you have other jobs or significant income outside your main employment. Your employer uses this information plus IRS withholding tables to calculate how much federal tax to take from each paycheck.

If you claim zero dependents and have no other income, your employer withholds more federal tax per paycheck. If you claim dependents or have income that reduces your tax liability, less is withheld. The goal is to withhold an amount close to what you will actually owe, though it is rarely exact.

You can update your W-4 at any time during the year — for example, if you get married, have a child, or take a second job. Changes take effect on the next paycheck after your employer processes the new form. Many people adjust their W-4 in late fall if they realize they are getting a large refund, or in early spring if they owe money at tax time.

State and local income tax withholding

Forty-one states and the District of Columbia have an income tax. Nine states (Alaska, Florida, Nevada, South Dakota, Tennessee, Texas, Washington, Wyoming, and New Hampshire) do not. If you live and work in a state with income tax, your employer withholds a percentage of your wages for that state, separate from federal withholding.

State withholding rates vary widely. Some states use a flat percentage (for example, Illinois withholds 4.95% regardless of income), while others use a progressive system with multiple tax brackets like the federal system does. A few states have local income taxes on top of state tax — cities like New York, Philadelphia, and Columbus collect their own withholding.

If you work in one state but live in another, the rules depend on where you work. Most states tax income earned within their borders. Some states have reciprocal agreements that let you pay tax only to your state of residence. If you move during the year or work across state lines, you may need to file returns in multiple states.

What appears on your pay stub

Your pay stub shows gross pay (your total earnings before any deductions), then lists each withholding separately. You will see a line for Social Security tax, Medicare tax, federal income tax, and state income tax (if applicable). Some pay stubs also show your year-to-date totals for each withholding, which is useful for tracking whether the right amount has been taken so far.

The pay stub also shows any voluntary deductions — health insurance premiums, 401(k) contributions, or flexible spending account deposits. These are taken out before federal income tax is calculated, which means they reduce your taxable income. For example, if you contribute $200 per paycheck to a traditional 401(k), that $200 is subtracted from your gross pay before your employer calculates federal withholding.

Your net pay (take-home pay) is your gross pay minus all withholdings and deductions. This is the amount that actually deposits into your bank account.

Why your withholding might be wrong

Withholding is an estimate based on the information you provided on your W-4. It can be wrong for several reasons. If you have a spouse who also works, you may be over-withheld because the W-4 does not account for your spouse's income. If you have a second job, your withholding from both jobs combined may be too high or too low. If you have significant investment income or self-employment income, that is not reflected in your W-4 at all.

Life changes also affect withholding. Getting married, having a child, or adopting a dependent changes your tax liability, but your withholding stays the same until you submit a new W-4. The same is true if you pay off a mortgage or student loans — your tax liability changes, but your employer does not know unless you tell them.

The IRS provides a Withholding Estimator tool on its website (irs.gov) that lets you calculate whether your current withholding is close to your actual tax liability. If it is not, you can adjust your W-4 to increase or decrease the amount withheld.

Self-employment taxes and quarterly payments

If you are self-employed or have income from freelance work, gig work, or a business, you do not have an employer to withhold taxes for you. Instead, you pay self-employment tax quarterly using Form 1040-ES. Self-employment tax covers both the employee and employer portions of Social Security and Medicare, totaling 15.3% of your net self-employment income (after business expenses).

Quarterly estimated tax payments are due on April 15, June 15, September 15, and January 15 of the following year. If you do not pay quarterly and owe a large amount at tax time, you may owe a penalty for underpayment. Many self-employed people set aside a percentage of each payment they receive to cover taxes, then make the quarterly payment from that reserve.

Self-employed people also file Schedule C (Profit or Loss from Business) with their tax return to report income and expenses. This is more complex than W-2 withholding, and many self-employed people work with a tax professional to make sure they are paying the right amount.

Frequently Asked Questions

Why do I get a refund if taxes were already taken from my paycheck?

Your employer withholds an estimate based on your W-4, but your actual tax liability depends on your total income, deductions, and credits for the year. If you claimed too many dependents on your W-4 or had life changes you did not report, less was withheld than you actually owed — or more was withheld than you owed, resulting in a refund. Filing your tax return calculates the exact amount, and the IRS adjusts the difference.

Can I stop taxes from being withheld from my paycheck?

No. Social Security and Medicare withholding is mandatory for all employees. Federal income tax withholding is also mandatory, though you can adjust how much is withheld by updating your W-4. You cannot claim exempt status to avoid all withholding unless you had no tax liability last year and expect none this year — and even then, the exemption expires after one year.

What happens if my employer withholds the wrong amount?

If your employer withholds too much, you will receive a refund when you file your tax return. If your employer withholds too little, you will owe the difference. You can also adjust your W-4 during the year to correct the withholding going forward. Use the IRS Withholding Estimator to see if your current withholding is on track.

Do I pay taxes on my 401(k) contributions?

Contributions to a traditional 401(k) are not subject to federal income tax when you make them — they reduce your taxable income for the year. However, you will pay income tax on the money when you withdraw it in retirement. Roth 401(k) contributions are made with after-tax money, so withdrawals in retirement are tax-free.

What if I work in multiple states during the year?

You may owe income tax to more than one state. Most states tax income earned within their borders. When you file your tax return, you typically file in your state of residence and claim a credit for taxes paid to other states to avoid double taxation. Some states have reciprocal agreements that simplify this process. A tax professional can help if you worked in multiple states.