US payroll taxes explained: federal income tax and FICA

A US paycheck is shrunk by several separate taxes before it reaches you: federal income tax, the two FICAtaxes (Social Security and Medicare), and — in most states — state income tax. This guide covers the federal and FICA pieces that apply almost everywhere; state tax, which varies enormously, has its own guide.

Federal income tax: brackets and the standard deduction

Federal income tax is progressive: your income is sliced into brackets and each slice is taxed at its own rate (10%, 12%, 22%, 24%, 32%, 35% and 37% for 2025). Crucially, you are not taxed on your whole salary — the standard deduction ($15,000 for a single filer in 2025) comes off first, and only what remains is run through the brackets. As with the UK, moving into a higher bracket only raises the rate on the dollars inside that bracket, not on your entire income.

FICA: Social Security and Medicare

On top of income tax, every employee pays two flat FICA taxes, withheld automatically:

• Social Security— 6.2% of wages, but only up to an annual wage base ($176,100 for 2025). Earnings above the cap pay no further Social Security tax.
• Medicare— 1.45% of all wages, with no cap. High earners pay an extra 0.9% Additional Medicare tax on wages above $200,000.

Your employer quietly matches the 6.2% and 1.45% — a cost that never appears on your payslip but is part of what it costs to employ you. FICA is why even a low earner with little federal income tax still sees a meaningful chunk withheld.

Putting it together

For a single filer, the rough order each pay period is: start with gross, subtract pre-tax deductions (see 401(k), HSA and friends), apply the standard deduction and federal brackets for income tax, add 6.2% + 1.45% FICA, and then subtract any state income tax. What is left is your take-home. You can see the full federal + FICA + state breakdown for any salary on the US take-home pay calculator — for example a $75,000 salary in California.

The takeaways

Federal income tax is progressive and only bites after the standard deduction; FICA is flat, automatic, and (for Social Security) capped. Together they explain most of the gap between your offer letter and your bank balance — before your state takes its share. To see how much that last piece varies, read why take-home pay differs by state. Figures here are 2025 single-filer; your filing status and state will change them.