What gets subtracted from your gross pay

Your employer calculates payroll taxes by starting with your gross pay — the total amount you earned before any deductions — and then subtracting federal income tax, Social Security tax, Medicare tax, and any state or local income taxes that explore where you work or live. The math is straightforward, but the rates and rules vary by your situation, your state, and how much you earn.

Federal income tax is withheld based on the W-4 form you filled out when you were hired. That form tells your employer how many allowances to claim, which directly affects how much federal tax comes out of each check. Social Security and Medicare are fixed percentages: 6.2% for Social Security (on earnings up to a cap that changes each year) and 1.45% for Medicare (on all earnings). Your employer also pays an equal amount of these taxes on your behalf, though you do not see that deduction on your stub.

State and local income taxes work differently depending on where you live. Some states have no income tax at all. Others withhold a percentage based on your income, filing status, and dependents — often using a form similar to the federal W-4. A few states use a flat percentage. Your employer is required to withhold only if your state or locality has an income tax.

Key Takeaways

  • Federal income tax withholding is based on your W-4 form, which you can update anytime if your life changes or you want more or less withheld each pay period.
  • Social Security tax is 6.2% of your wages up to an annual cap (which increases yearly), and Medicare tax is 1.45% of all wages with no cap.
  • State and local income tax withholding varies by location — some states have no income tax, while others withhold a percentage based on your filing status and dependents.
  • Your employer withholds taxes and sends them to the IRS and your state on your behalf; the amount withheld is not the same as what you actually owe at tax time.
  • If too much or too little is withheld, you will either owe money or receive a refund when you file your tax return.

How the W-4 controls federal withholding

The Form W-4 is the document that tells your employer how much federal income tax to take out of each paycheck. When you start a job, you complete it by providing your name, address, filing status (single, married, head of household), number of dependents, and any other income sources. Your employer uses this information to calculate a withholding amount for each pay period.

If you want to change your withholding — because you got married, had a child, took a second job, or straightforward want less withheld — you can submit a new W-4 to your employer at any time. The change takes effect on your next paycheck. Many people update their W-4 in January or after a major life event, but you can do it whenever your situation changes.

The W-4 does not determine your final tax bill. It only determines how much your employer holds back during the year. When you file your tax return in April, you report your actual income and calculate what you actually owe. If your employer withheld too much, you get a refund. If too little was withheld, you owe the difference.

Social Security and Medicare tax calculations

Social Security and Medicare taxes are calculated as fixed percentages of your wages. Social Security tax is 6.2% of your gross pay, but only on earnings up to a limit set by the Social Security Administration. That limit changes each year — in 2024 it was $168,600, but it increases annually based on wage growth. Once you hit that cap in a calendar year, no more Social Security tax is withheld from your remaining paychecks that year.

Medicare tax is 1.45% of all your wages with no upper limit. So if you earn $200,000 in a year, you pay Medicare tax on the full $200,000. However, if your income exceeds certain thresholds ($200,000 for single filers, $250,000 for married filing jointly), an additional 0.9% Medicare tax applies to the amount over the threshold. Your employer withholds this extra tax automatically if you cross that line.

Both Social Security and Medicare are FICA taxes (Federal Insurance Contributions Act). Your employer withholds your share and also pays an equal share on your behalf. You see only your half on your pay stub, but the employer's half is a real cost to the business.

State and local income tax withholding

State income tax withholding depends entirely on where you live and where you work. If you live in a state with no income tax — such as Florida, Texas, Wyoming, or South Dakota — your employer will not withhold state income tax. If you live in a state that does tax income, your employer will withhold based on a state form you complete, often called a state W-4 or equivalent.

Some states use a percentage-based system similar to federal withholding, where you claim allowances or dependents. Others use a flat percentage of your gross pay. A few states allow you to claim an exemption if you expect to owe no state tax that year. The rules vary significantly, so check your state's tax authority website or ask your employer's payroll department what form you need to complete.

Local income taxes exist in some cities and counties, particularly in Ohio, Pennsylvania, and parts of other states. If your workplace is in a locality with an income tax, your employer will withhold that as well. The rate and rules are set by the local government, not the state.

Reading your pay stub to verify the calculation

Your pay stub shows the calculation step by step. It lists your gross pay at the top, then subtracts each tax and deduction line by line. You should see federal income tax, Social Security (labeled as "FICA-SS" or "OASDI"), Medicare (labeled as "FICA-Med" or "HI"), and any state or local income tax. Some pay stubs also show the employer's matching taxes, though those do not reduce your take-home pay.

To verify the math yourself: multiply your gross pay by the Social Security percentage (6.2%) up to the annual cap, then by the Medicare percentage (1.45%), then check that federal withholding matches your W-4 settings. If the numbers seem wrong — for example, if you see Social Security tax withheld after you hit the annual cap — contact your payroll department. Errors happen, and catching them early makes them easier to fix.

Keep your pay stubs throughout the year. They are the record of what was withheld, and you will need them if you file a tax return or if there is ever a dispute about your earnings or taxes paid.

What happens if withholding is wrong

If your employer withholds too much federal income tax during the year, you will receive a refund when you file your tax return. If too little is withheld, you will owe money. The difference between what was withheld and what you actually owe is settled when you file. This is why your withholding amount does not have to be perfect — the tax return is where the final calculation happens.

If you consistently owe money at tax time, you can update your W-4 to have less withheld, so you take home more each paycheck. If you consistently get a large refund, you can update your W-4 to have more withheld, so you get less back in April. Neither option changes your total tax bill for the year — it only changes the timing of when you pay.

Self-employed people and those with income not subject to withholding (such as investment income or rental income) often need to make estimated tax payments quarterly to avoid owing a large amount at tax time. Employees with withholding do not usually face this requirement, but if you have significant non-employment income, you may need to adjust your W-4 or make estimated payments.

When to update your W-4 or withholding

You should update your W-4 whenever your life changes in a way that affects your tax situation. Common reasons include getting married or divorced, having a child, taking a second job, your spouse starting or stopping work, or a major change in income. You can also update it if you straightforward want to adjust how much is withheld each pay period.

The IRS recommends reviewing your withholding at least once a year, particularly if you received a large refund or owed a large amount the previous year. You can use the IRS Withholding Calculator on the IRS website to estimate whether your current withholding is on track. It asks about your income, filing status, dependents, and other income sources, then tells you whether to adjust your W-4.

If you are unsure whether you need to make changes, or if your situation is complicated (multiple jobs, self-employment income, investment income), consider consulting a tax professional. They can review your specific circumstances and recommend a withholding strategy that minimizes surprises at tax time.

Frequently Asked Questions

Why is my Social Security tax withheld even though I might not collect benefits for decades?

Social Security tax funds current retirees and disabled workers, not just your own future benefits. The system is pay-as-you-go: your taxes today pay for today's beneficiaries, and future workers' taxes will pay for your benefits when you retire. You build a record of earnings that determines your benefit amount when you become may be able to access.

Can I claim zero allowances on my W-4 to get a bigger refund?

Yes, but it means more money is withheld from each paycheck, reducing your take-home pay. A larger refund does not mean you paid more tax overall — it means you overpaid during the year and are getting the overpayment back. Most people prefer to have the right amount withheld so they break even at tax time, rather than give the government an interest-free loan.

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

You typically owe income tax to the state where you work, not where you live, though some states have reciprocal agreements. Your employer will withhold based on your work location. When you file your tax return, you may need to file in both states and claim a credit to avoid double taxation. Check both states' tax authority websites or ask a tax professional for your specific situation.

Does my employer's matching tax come out of my paycheck?

No. Your employer pays their matching Social Security and Medicare taxes separately from your paycheck. You see only your half (6.2% Social Security and 1.45% Medicare) deducted from your gross pay. The employer's half is a business expense that does not reduce your take-home pay.

What if my employer withholds the wrong amount of state tax?

Contact your payroll department and provide an updated state W-4 or withholding form. If the error is not corrected, you will catch it when you file your state tax return and can claim a credit for overpayment or pay the underpayment. Keep records of all pay stubs and correspondence with payroll in case you need to dispute the amount later.