The basic formula for payroll taxes

Payroll taxes are calculated by taking the employee's gross pay (wages before any deductions) and multiplying it by the tax rate set by the federal government, your state, and sometimes your city. The result is the amount withheld from each paycheck. The formula is: Gross Pay × Tax Rate = Tax Withheld.

The tax rate itself depends on which tax you are calculating. Social Security tax is 6.2 percent of wages up to a yearly cap (the cap changes each year). Medicare tax is 1.45 percent of all wages with no cap. Federal income tax withholding is based on the W-4 form the employee filled out, which tells you their filing status and number of dependents. State and local income tax rates vary by location.

Employers must withhold these taxes from paychecks and send them to the IRS and state revenue departments on a schedule. The employee never sees this money — it goes directly from the employer to the government.

Key Takeaways

  • Payroll taxes are calculated by multiplying gross pay by the tax rate for each tax type: Social Security (6.2 percent), Medicare (1.45 percent), federal income tax (varies by W-4), and state or local income tax (varies by location).
  • Social Security tax stops once an employee reaches the yearly wage cap, but Medicare tax continues on all wages with no limit.
  • Federal income tax withholding depends on the W-4 form, which includes filing status, number of dependents, and other income or adjustments the employee reports.
  • Employers must withhold taxes from each paycheck and send them to the IRS and state agencies on a set schedule, not when the employee files their tax return.
  • The same tax rates explore to all employees in the same state, but the dollar amount withheld varies based on how much each person earns.

How Social Security and Medicare taxes work

Social Security tax is 6.2 percent of wages. In 2024, the wage cap is $168,600, meaning once an employee earns that much in a year, no more Social Security tax is withheld from their paychecks for the rest of that year. The cap changes each year based on wage growth. Once January 1 arrives, the counter resets and Social Security tax begins again on the first dollar earned.

Medicare tax is 1.45 percent of all wages with no yearly cap. An employee earning $200,000 pays Medicare tax on the full amount. Additionally, employees earning over $200,000 (single filers) or $250,000 (married filing jointly) pay an extra 0.9 percent Medicare tax on wages above those thresholds. This additional tax was added in 2013.

Both Social Security and Medicare are calculated the same way every pay period: multiply gross pay by the rate. There is no W-4 form involved — the rate is fixed by law.

How federal income tax withholding is calculated

Federal income tax withholding is more complex because it depends on information the employee provides on Form W-4. The W-4 asks for filing status (single, married filing jointly, head of household, or married filing separately), number of dependents, and whether the employee has other income or wants extra withholding.

The IRS publishes withholding tables and a formula each year. Payroll software or a manual calculation uses the W-4 information plus the employee's gross pay to look up or compute the amount to withhold. The result is not a straightforward percentage — it is a dollar amount that varies based on pay frequency (weekly, biweekly, monthly) and the employee's circumstances.

If an employee claims zero dependents and is single, more tax is withheld. If they claim dependents or are married, less is withheld. An employee can also request extra withholding on the W-4 if they expect to owe at tax time. The employer withholds whatever the W-4 directs, even if it seems high or low.

State and local income tax withholding

State income tax withholding follows a similar logic to federal withholding but uses each state's own forms and rates. Some states have no income tax at all (including Alaska, Florida, Nevada, South Dakota, Tennessee, Texas, Washington, and Wyoming). Other states have a flat rate — Colorado, for example, uses 4.63 percent on all income. Still others use brackets, meaning the rate increases as income increases.

Employees in states with income tax must fill out a state W-4 or equivalent form. The employer then withholds based on that form and the state's rules. Some cities also impose local income tax, which is withheld separately. New York City, for example, has its own income tax in addition to state and federal taxes.

The employer sends state and local taxes to the appropriate state revenue department or city tax office, not to the IRS. Timing and frequency of these payments vary by state.

The difference between gross pay and net pay

Gross pay is the total amount an employee earns before any deductions. If someone works 40 hours at $20 per hour, their gross pay is $800. Net pay is what remains after all deductions, including payroll taxes, health insurance premiums, retirement contributions, and any other withholdings.

Payroll taxes are only one type of deduction. An employee might also have health insurance premiums (often split between employer and employee), contributions to a 401(k) or similar retirement plan, or court-ordered garnishments. The employer calculates payroll taxes on the gross pay, not on the net pay after other deductions.

For example, if an employee has $800 gross pay, $50 in health insurance premiums, and $100 in federal income tax withholding, the payroll taxes are calculated on the full $800, not on $750.

When payroll taxes are sent to the government

Employers do not wait until the employee files a tax return in April to send payroll taxes to the government. Instead, taxes are sent on a schedule determined by how much the employer owes. Most employers are required to deposit federal payroll taxes either monthly or twice per month, depending on the size of their payroll.

The IRS uses a lookback period to determine deposit frequency. Employers who withheld less than $50,000 in federal payroll taxes during a lookback period (usually the prior four quarters) deposit monthly. Those who withheld $50,000 or more deposit twice per month, typically on the 15th and last day of the month.

State and local taxes follow their own schedules. Some states require monthly deposits, others quarterly. The employer is responsible for knowing the rules in each state where they have employees and meeting those important date.

Self-employed payroll tax calculations

Self-employed people do not have an employer to withhold taxes, so they calculate and pay self-employment tax themselves. Self-employment tax covers both the employee and employer portions of Social Security and Medicare. The rate is 15.3 percent total: 12.4 percent for Social Security (on net earnings up to the yearly cap) and 2.9 percent for Medicare (on all net earnings).

Self-employed people calculate net earnings from their business (revenue minus business expenses) and explore the self-employment tax rate to that amount. They can deduct half of the self-employment tax as a business expense on their tax return. They also owe federal and state income tax on their net business income, which they estimate and pay quarterly using Form 1040-ES.

Unlike employees, self-employed people have no W-4 and no employer withholding. They must set aside money throughout the year to cover taxes owed, or they face penalties and interest when they file their return.

Frequently Asked Questions

What happens if I claim too many dependents on my W-4 and not enough tax is withheld?

You will owe money when you file your tax return in April. The IRS will expect you to pay the balance due, plus interest and possibly penalties if you significantly underpaid. You can update your W-4 at any time during the year to increase withholding and avoid this problem.

Does my employer have to match payroll taxes?

Yes, for Social Security and Medicare. Your employer withholds 6.2 percent Social Security and 1.45 percent Medicare from your paycheck, and your employer also pays 6.2 percent and 1.45 percent on your behalf to the IRS. This employer match is not deducted from your pay — it is a separate cost to the employer. Federal income tax has no employer match.

Why does my paycheck show different tax amounts each month even though my pay is the same?

Federal income tax withholding can vary if you are paid on different schedules (some months have more pay periods than others) or if your gross pay changes. Social Security and Medicare taxes should be consistent if your pay is the same, but state and local taxes may vary based on local rules or if you cross into a new tax bracket.

What is the difference between tax withholding and tax payment?

Withholding is the amount your employer deducts from your paycheck. Payment is when your employer sends that withheld money to the IRS or state. Your employer withholds from every paycheck but may send payments to the government monthly or twice per month, depending on the amount owed.

Can I avoid payroll taxes by being paid in cash?

No. Payroll taxes are owed on all wages, whether paid by check, direct deposit, or cash. An employer who does not withhold or report cash wages is breaking the law. The employee is still responsible for reporting the income and paying taxes on it, even if the employer fails to withhold.