Your pay stub decoded — and the W-4 behind it

Your first paycheck arrives and you instantly notice a gap between what you expected and what actually hit your bank account. That difference—sometimes 20% to 35% of your gross pay—is the combined effect of federal tax withholding, Social Security and Medicare taxes, state income tax, and any voluntary deductions you have set up. Your W-4 form controls the biggest slice of that gap: the federal income tax. Understanding what leaves your paycheck and why is essential to managing your money, filing your taxes correctly, and spotting errors before they compound.

Gross Pay vs. Net Pay: What You Actually Take Home

Gross pay is the total amount you earn before any deductions. If you earn USD 15 per hour and work 40 hours, your gross pay is USD 600. Net pay is what lands in your account: gross pay minus all taxes and deductions. If USD 100 in taxes and benefits are withheld, your net pay is USD 500.

The gap exists because the U.S. federal government collects income tax gradually throughout the year by withholding from each paycheck, rather than waiting for you to file your tax return in April. FICA taxes (Social Security and Medicare) are also mandatory and are withheld at fixed rates. State and local income taxes, where they apply, add another layer. When you combine federal withholding, FICA taxes, and state or local income tax, expect roughly 20% to 35% of your gross pay to disappear, depending on your income level, the state you work in, your filing status, and the number of dependents you claim.

The W-4: Your Tool to Control Federal Withholding

Form W-4, officially the Employee's Withholding Certificate, is the document you complete when you start a job. It tells your employer how much federal income tax to withhold from each paycheck. The IRS releases an updated version of the form each year, and the most recent major redesign occurred in 2020, when the agency removed the old allowances system and simplified the form to make it easier to use.

What Information You Provide on a W-4

Step 1 asks for your personal information: name, address, and Social Security Number (SSN). Make sure your name matches exactly what appears on your Social Security card. If it does not, contact the Social Security Administration at 800-772-1213 or visit www.ssa.gov to correct it before submitting the form—errors here can prevent you from getting credit for your earnings.

Step 2 asks you to select your filing status: single, married filing jointly, married filing separately, or head of household. This directly affects how much federal tax will be withheld. Married couples filing jointly typically have less tax withheld than two single filers with the same combined income.

Steps 3 and 4 capture your dependents and other income sources. If you claim dependents on your tax return, entering them reduces your federal withholding. If you work more than one job, have a spouse who works, or earn income from investments or self-employment, the form offers options to account for that so your withholding is accurate.

When to Update Your W-4

Life changes make a W-4 update necessary. Major events that warrant a new form include marriage, divorce, birth of a child, starting a second job, receiving a large tax refund (meaning too much was withheld), or owing a tax bill at the end of the year (meaning too little was withheld). Filing a new W-4 takes just a few minutes and can prevent you from giving the government an interest-free loan or facing an unexpected tax bill.

The IRS offers a Tax Withholding Estimator tool on its website to help you determine whether your current withholding is correct. If you discover you need to adjust, submit a new W-4 to your payroll department as soon as possible; the change typically takes effect in your next paycheck or within a few pay periods.

The Main Deductions on Your Pay Stub

Federal Income Tax Withholding

This is the largest deduction on most pay stubs. The amount withheld depends on your gross pay, your filing status, the number of dependents you claim, and any adjustments you specify on your W-4. Federal income tax uses a progressive bracket system, meaning higher income is taxed at higher rates. Your employer uses IRS-approved methods to calculate the correct withholding for each paycheck.

FICA Taxes: Social Security and Medicare

FICA stands for the Federal Insurance Contributions Act. These are fixed-percentage payroll taxes that fund Social Security and Medicare. Your employer withholds 6.2% of your wages for Social Security and 1.45% for Medicare, for a total of 7.65%. Your employer then matches these amounts and pays an additional 7.65% to the government on your behalf, for a combined total of 15.3% of your pay flowing into these programs.

On your pay stub, FICA taxes may appear as separate line items labeled Social Security, OASDI (Old-Age, Survivors, and Disability Insurance), Medicare, or simply FICA-SS and FICA-Med. Note that the Social Security portion has an annual wage cap: in 2026, you pay Social Security tax only on wages up to USD 184,500. Once you cross that threshold in a calendar year, the 6.2% Social Security withholding stops, but the 1.45% Medicare tax continues on all wages. High earners pay an additional 0.9% Medicare tax on wages above USD 200,000.

State and Local Income Tax

State income tax withholding varies dramatically by location. Seven U.S. states levy no individual income tax at all. Many others use a flat tax rate, while most apply graduated rates similar to the federal system. Some states tax only certain types of income. Your state may also impose a local income tax depending on your city or county. Check your state's Department of Revenue or tax commission website to learn the rules in your state and what rate applies to your income.

If you work in one state but live in another—a common situation for remote workers and commuters—you may owe tax to both states. Some states offer reciprocal agreements or credits to avoid double taxation, but the rules differ widely. When relocating or starting a remote job, research the tax obligations in both your home state and the state where your employer is based.

Other Common Deductions

Beyond taxes, your pay stub may show pre-tax and post-tax deductions. Pre-tax deductions—such as contributions to a traditional 401(k) retirement plan, health insurance premiums, or a health savings account (HSA)—reduce your taxable income and are withheld before federal and state income tax is calculated, lowering your overall tax burden. Post-tax deductions, such as contributions to a Roth 401(k) or certain insurance products, are taken out after taxes.

• Health insurance premiums (pre-tax if through employer)
• Dental and vision insurance
• Life insurance
• 401(k) or other retirement plan contributions (typically pre-tax)
• Health Savings Account (HSA) contributions (pre-tax)
• Flexible Spending Account (FSA) for dependent care
• Union dues
• Wage garnishments or child support orders (post-tax, mandatory)
• Charitable donations (if you enroll in payroll giving)

How to Read Your Pay Stub

Most pay stubs follow a similar layout, though the order may vary. At the top, you'll see your employer's name and your personal information. The pay period dates show when you worked and when you will be paid. Then comes the earnings section, typically labeled Gross Pay, showing your hourly rate or salary, hours worked, regular pay, overtime, and bonuses. This section should list both the current pay period total and a year-to-date (YTD) cumulative amount.

Below earnings, you'll find deductions divided into tax and benefit categories. Each line item shows the current amount withheld and the YTD total. At the bottom is your net pay or take-home pay—the amount you actually receive after all deductions.

Many pay stubs also include an employer contributions section, showing what your company pays on your behalf for benefits like health insurance, retirement matching, or workers' compensation insurance. These are not subtracted from your paycheck, but they represent real compensation you are receiving.

Checking for Errors

Review your pay stub every pay period, even if you use direct deposit and never see the paper version. Check that your personal information and employee ID are correct. Verify your hours worked match what you actually worked, and confirm your hourly rate or salary is accurate. Look at gross pay and ensure it aligns with your expected earnings.

Then scrutinize the deductions. If you did not enroll in a benefit or change your W-4, an unexpected deduction is a red flag. Payroll errors are common and are often easiest to fix immediately when caught. If you spot a mistake—duplicate deduction, missing overtime, or incorrect withholding—report it to your human resources or payroll department right away. Most errors can be corrected with a simple adjustment on the next paycheck.

Keep a copy of each pay stub. You'll need them to verify income on loan applications, rental applications, and tax filings. Your year-end W-2 form, which your employer must provide by January 31, summarizes all your pay and withholding for the calendar year and is the document you'll use when filing your federal tax return.

Special Situations for Immigrants and Visa Holders

If you do not yet have a Social Security Number (SSN) but have a valid work visa or green card, you may be issued an Individual Taxpayer Identification Number (ITIN) by the IRS. On your W-4, you can enter your ITIN in place of an SSN. Once you receive your SSN, notify your employer and payroll department immediately so they can update their records and ensure your earnings are properly credited to your Social Security account.

Nonresident aliens on work visas may have different tax withholding rules than U.S. citizens and permanent residents. Some visa categories require special tax treatment. Consult with a tax professional or the IRS if you are unsure whether you qualify as a resident or nonresident alien for tax purposes, as this affects your filing requirements and withholding obligations.

If you worked in another country before moving to the U.S., those earnings do not count toward your U.S. Social Security record. The U.S. has Social Security totalization agreements with certain countries that allow you to combine credits from both countries to qualify for benefits, but you must apply separately. Research whether your country of origin has such an agreement with the U.S.

Key Takeaways

• Gross pay is what you earn; net pay is what you take home after taxes and deductions. Expect 20% to 35% of gross pay to be withheld.
• Your W-4 form controls federal income tax withholding. Update it after major life changes—marriage, a second job, birth of a child, or when you owe tax or receive a large refund.
• FICA taxes (Social Security and Medicare) are a fixed 7.65% from your pay and are not adjustable via the W-4.
• State income tax varies by state; some states have no income tax at all. Check your state's rules.
• Review your pay stub every pay period. Check hours, rates, deductions, and personal information. Payroll errors are common and easiest to fix immediately.
• Keep copies of all pay stubs and your year-end W-2 for tax filing, loan applications, and your records.