What payroll tax is and why it comes out of your check

Payroll tax is money withheld from your paycheck by your employer and sent to federal and state governments. It covers Social Security, Medicare, and income tax. The amount depends on your gross pay (what you earn before deductions), your filing status, and how many dependents you claim on your W-4 form.

Your employer is required by law to withhold these taxes and remit them on your behalf. You do not pay them separately — they come directly from your paycheck. The withholding is an advance payment toward your annual tax bill. When you file your tax return, the IRS compares what was withheld to what you actually owe, and you either get a refund or owe more.

Key Takeaways

  • Federal income tax withholding depends on your W-4 form, which you fill out when hired or update when your situation changes.
  • Social Security tax is 6.2% of your gross pay up to a yearly cap (the cap changes annually), and Medicare tax is 1.45% with no cap.
  • State and local income tax withholding varies by where you live and work, and some states have no income tax at all.
  • Your paycheck stub shows gross pay, each tax withheld, and net pay (what you take home), so you can track what is being deducted.

Federal income tax withholding and your W-4 form

Federal income tax withholding is calculated using the W-4 form you complete when you start a job. The form asks for your filing status (single, married, head of household), number of dependents, and other income sources. Your employer uses this information and IRS withholding tables to determine how much federal tax to take from each paycheck.

If you claim zero dependents and file as single, more tax is withheld. If you claim dependents or file as married, less is withheld. You can update your W-4 whenever your situation changes — a marriage, divorce, new child, second job, or spouse starting work. The more accurate your W-4, the closer your withholding will be to your actual tax bill, and the smaller your refund or balance due will be at tax time.

The IRS publishes updated withholding tables each year, and employers use the current tables for that year. If you want to estimate your withholding, you can use the IRS Withholding Calculator on irs.gov, which asks questions about your income, filing status, and deductions to show you whether you are withholding too much or too little.

Social Security and Medicare tax (FICA)

FICA stands for Federal Insurance Contributions Act and covers two programs. Social Security tax is 6.2% of your gross pay, but only up to a yearly wage cap. Medicare tax is 1.45% of your gross pay with no cap. Both are withheld from every paycheck.

The Social Security wage cap changes each year. In 2024, for example, only the first $168,600 of your annual income is subject to the 6.2% Social Security tax. Once you reach that cap in a year, no more Social Security tax is withheld from your remaining paychecks that year. Medicare tax, by contrast, continues on every dollar you earn. If you earn over $200,000 (single) or $250,000 (married filing jointly), an additional 0.9% Medicare tax is withheld.

FICA taxes fund Social Security retirement benefits, disability benefits, and Medicare health insurance for people 65 and older. Your employer also pays an equal amount (6.2% Social Security and 1.45% Medicare) on your behalf, though this does not appear on your paycheck.

State and local income tax withholding

State income tax withholding varies by where you live and work. Most states have an income tax and withhold it from paychecks using a state W-4 form or similar document. Some states — including Texas, Florida, Nevada, South Dakota, Tennessee, Washington, and Wyoming — have no state income tax at all, so nothing is withheld.

If you live in one state and work in another, you typically withhold based on where you work. Some states have reciprocal agreements that let you withhold based on your home state instead. Local income taxes exist in some cities and counties and are withheld the same way. Your paycheck stub will show each tax withheld separately, so you can see what goes to federal, state, and local governments.

State withholding tables and rules change periodically, so if you move or change jobs, ask your new employer for the current state W-4 form. You can also contact your state's tax department directly to confirm the withholding rules for your situation.

Reading your paycheck stub and understanding deductions

Your paycheck stub (or pay stub) is a document that breaks down your pay and deductions. It shows your gross pay (total earnings before any deductions), each tax withheld (federal, Social Security, Medicare, state, local), other deductions (health insurance premiums, retirement contributions, garnishments), and your net pay (what you actually receive).

The stub also shows year-to-date totals, which track how much you have earned and how much has been withheld so far in the calendar year. This is useful for checking whether your withholding is on track. If you are self-employed or have a second job, year-to-date totals help you estimate your total tax bill before filing your return.

Some deductions are taxes (federal, state, Social Security, Medicare). Others are not taxes but are still withheld — health insurance premiums, 401(k) contributions, and court-ordered garnishments. Tax deductions reduce your taxable income. Non-tax deductions reduce your take-home pay but do not affect your tax bill. Your paycheck stub should label each one clearly.

How to calculate your own withholding

To estimate federal income tax withholding, start with your gross pay for one paycheck. Multiply it by the number of pay periods in a year (26 for biweekly, 24 for semimonthly, 52 for weekly, 12 for monthly). This gives you your estimated annual gross income.

Next, use the IRS Withholding Calculator (irs.gov/taxes/individuals/tax-withholding-estimator) or the tax tables in IRS Publication 15-T. The calculator asks about your filing status, dependents, other income, and deductions, then tells you how much federal tax should be withheld per paycheck. If your actual withholding does not match, you can adjust your W-4.

For Social Security and Medicare, the math is simpler. Multiply your gross pay by 6.2% for Social Security (up to the annual wage cap) and 1.45% for Medicare. These rates are fixed and do not change based on your W-4. State and local taxes vary by location, so check your state tax department's website for the current rates and withholding tables.

What happens if too much or too little is withheld

If too much tax is withheld throughout the year, you will receive a refund when you file your tax return. If too little is withheld, you will owe money. Neither is ideal — a large refund means you gave the government an interest-free loan, and owing money means you may owe penalties and interest if you do not pay by the deadline.

To adjust your withholding during the year, fill out a new W-4 and give it to your employer's payroll department. You can do this as many times as needed. If you expect a big refund, you might increase your dependents or claim an adjustment to reduce withholding. If you expect to owe, you might reduce your dependents or claim an adjustment to increase withholding.

The goal is to have your withholding match your actual tax bill as closely as possible. This takes some trial and error, especially if your income varies or you have multiple jobs. The IRS Withholding Calculator is the most accurate tool for this, and you can use it anytime your situation changes.

Frequently Asked Questions

Why does my paycheck stub show different amounts withheld each month?

If your pay varies (hourly work, commissions, bonuses), your gross pay changes, and so do your tax withholdings. Federal income tax is calculated as a percentage of gross pay, so a bigger paycheck means more withheld. Social Security and Medicare are also percentages, so they fluctuate with your pay. Bonuses and overtime can cause significant swings.

What is the difference between tax withholding and tax deductions?

Withholding is money taken from your paycheck and sent to the government as an advance payment on your taxes. Deductions are expenses you subtract from your income when you file your tax return to lower your taxable income. They are separate things — withholding happens during the year, deductions happen at tax time.

Can I claim exempt from federal income tax withholding?

You can claim exempt only if you had no tax bill last year and expect no tax bill this year. If you claim exempt, no federal income tax is withheld from your paycheck, but Social Security and Medicare still are. Most people should not claim exempt because they will owe a large bill at tax time. The IRS can penalize you if you claim exempt incorrectly.

Do I have to fill out a W-4 every time I change jobs?

Yes. Each employer needs a W-4 to know how much federal tax to withhold. When you start a new job, your employer will ask you to complete one. You can use the same W-4 information from your previous job, or update it if your situation has changed. Keep a copy for your records.

What if I work in one state but live in another?

You typically withhold based on the state where you work. However, some states have reciprocal agreements that allow you to withhold based on your home state instead. Check with your employer's payroll department or your state's tax department to confirm which rule applies to you.