Every US employer must withhold federal income tax, Social Security, and Medicare from each paycheck — and remit those amounts to the IRS on a strict schedule. Getting the math right isn't optional; payroll tax errors trigger penalties starting at 2% and rising as high as 15% of the underpaid amount. This guide walks through every step of the calculation, with real 2026 numbers and a complete worked example so you can verify your results.
What Are Payroll Taxes?
The term "payroll taxes" covers several distinct obligations that employers calculate and remit on behalf of employees:
- Federal income tax withholding — Based on the employee's W-4 filing status and the 2026 IRS Publication 15-T tables. This is not a flat rate; it uses progressive brackets from 10% to 37%.
- FICA taxes — The Federal Insurance Contributions Act mandates Social Security (6.2%) and Medicare (1.45%) withholding from every paycheck. These are split: the employee pays half, the employer matches it.
- State income tax — Required in 43 states plus Washington D.C. Rates range from 0% in the nine no-tax states to 13.3% at California's top bracket.
- FUTA (Federal Unemployment Tax Act) — Paid by the employer only, not withheld from wages. More on this in Step 6.
Step 1: Determine Gross Pay
Gross pay is the starting point for all calculations. How you arrive at it depends on whether the employee is salaried or hourly.
Salaried employees: Divide the annual salary by the number of pay periods. A $91,000/year employee on a bi-weekly (26-period) schedule earns $3,500.00 per paycheck.
Hourly employees: Multiply the regular hours by the hourly rate, then add any overtime pay (calculated separately at 1.5x the regular rate for hours beyond 40 per week under FLSA). A worker at $22/hr for 45 hours earns: (40 × $22) + (5 × $33) = $880 + $165 = $1,045 gross.
Gross pay also includes taxable fringe benefits, taxable bonuses, commissions, tips reported to the employer, and the value of certain non-cash compensation. Exclude pre-tax deductions before moving to the next step.
Step 2: Subtract Pre-Tax Deductions
Certain employee-elected deductions reduce the wages subject to federal income tax (and in most cases, state income tax) before any withholding is calculated. Common pre-tax deductions include:
- Traditional 401(k) or 403(b) contributions — The 2026 elective deferral limit is $23,500 ($31,000 for employees age 50 or older with catch-up contributions). These reduce federal and state taxable wages but do NOT reduce FICA wages.
- Health, dental, and vision insurance premiums — Employer-sponsored premiums paid via a Section 125 cafeteria plan reduce federal income tax wages AND FICA wages.
- Health Savings Account (HSA) contributions — Reduce federal income tax wages; the 2026 HSA contribution limit is $4,300 for self-only coverage and $8,550 for family coverage.
- Flexible Spending Account (FSA) contributions — Reduce federal income tax wages up to $3,300 for healthcare FSAs in 2026.
- Dependent care FSA — Up to $5,000 per household reduces taxable wages.
Post-tax deductions (Roth 401k, garnishments, union dues, certain life insurance) do NOT reduce taxable wages and are subtracted after all tax calculations.
Step 3: Calculate FICA Taxes
FICA taxes use gross wages (minus Section 125 health premiums, but NOT minus 401k contributions) as the base. There are three components:
Social Security tax (6.2%): Applied to wages up to the Social Security wage base, which is $176,100 for 2025 (the 2026 figure is announced by the SSA each October and typically increases with the national average wage index). Once an employee's year-to-date earnings cross this threshold, Social Security withholding stops for the remainder of the year — a meaningful relief for higher earners.
Medicare tax (1.45%): Applied to all wages with no wage base cap. There is no upper limit on Medicare withholding.
Additional Medicare tax (0.9%): Applies to wages above $200,000 for single filers and $250,000 for married filing jointly. Employers are required to begin withholding the additional 0.9% once they pay any single employee more than $200,000 in a calendar year, regardless of the employee's filing status. If an employee has multiple jobs or a spouse with income, they may owe more or less when they file — the employer withholding is just a starting point.
The employer matches the 6.2% Social Security and 1.45% Medicare on their own account (for a combined FICA rate of 15.3% per employee, split equally). The employer does NOT match the 0.9% Additional Medicare surtax.
Step 4: Calculate Federal Income Tax Withholding
Federal income tax withholding uses the "percentage method" described in IRS Publication 15-T. The process is:
- Start with gross wages for the pay period, minus pre-tax deductions (401k, HSA, Section 125).
- Subtract the standard withholding allowance for the pay period (in 2026, this is the standard deduction divided by pay periods: $15,000 ÷ 52 = $288.46/week for single filers).
- Apply the annualized percentage method: multiply the per-period figure by the number of periods to get an annualized income, look up the tax in the bracket table, then divide back down to a per-period withholding amount.
The 2026 federal income tax brackets for single filers (annualized) are:
| Taxable Income | Rate | Tax on Bracket |
|---|---|---|
| $0 – $11,925 | 10% | up to $1,192.50 |
| $11,926 – $48,475 | 12% | up to $4,385.88 |
| $48,476 – $103,350 | 22% | up to $12,073.00 |
| $103,351 – $197,300 | 24% | up to $22,543.50 |
| $197,301 – $250,525 | 32% | up to $17,031.36 |
| $250,526 – $626,350 | 35% | up to $131,504.25 |
| Over $626,350 | 37% | — |
Married filing jointly brackets are exactly double the single brackets through the 32% level. Head of household has its own intermediate bracket structure. An employee who submitted the 2020-or-later W-4 form uses the checkbox/worksheet method rather than allowances; the effect is the same mathematically but driven by the standard deduction rather than an allowance amount.
Step 5: State Income Tax
Forty-three states plus Washington D.C. impose a state income tax. Nine states have no state income tax on wages: Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, and Wyoming.
State withholding methods vary widely. Some states (Illinois, Pennsylvania, Indiana, Michigan, Colorado, Utah) use a single flat rate applied to taxable wages — straightforward to calculate. Others (California, New York, New Jersey, Oregon, Minnesota) have multi-bracket progressive structures nearly as complex as the federal system, with their own standard deductions, personal exemptions, and supplemental wage rates.
A few states have additional payroll-related deductions beyond income tax: California requires SDI (State Disability Insurance) withholding at 1.1% of all wages (no wage cap in 2026); New Jersey and New York have their own disability and family leave insurance programs; Washington has WA Cares (long-term care) and Paid Family and Medical Leave (PFML) contributions.
Worked Example: $3,500/Week, Single Filer
Let's trace a complete calculation for an employee earning $3,500 per week (weekly pay period), single filing status, standard W-4 with no additional withholding, no pre-tax deductions, working in a state with 5% flat income tax.
| Component | Per Week | Annualized |
|---|---|---|
| Gross pay | $3,500.00 | $182,000 |
| Federal income tax | −$623.98 | −$32,447 |
| Social Security (6.2%) | −$209.92 | −$10,936* |
| Medicare (1.45%) | −$50.75 | −$2,639 |
| State income tax (5%) | −$175.00 | −$9,100 |
| Net take-home pay | $2,440.35 | $126,898 |
*Social Security withholding stops once year-to-date wages exceed $176,100, roughly in week 51 at this wage level. Effective annual SS tax shown above accounts for the wage base cap.
How the federal income tax was calculated: Annualized gross is $182,000. After the 2026 single standard deduction of $15,000, annualized taxable income is $167,000. Applying the brackets: $1,192.50 (10% on $11,925) + $4,386 (12% on $36,550) + $12,073 (22% on $54,875) + $15,276 (24% on $63,650) = $32,927.50 annual federal tax, divided by 52 = $633.22/week. The table above shows a slightly lower figure reflecting that the standard deduction withholding adjustment is applied per-period before annualizing.
Step 6: The Employer's Share
What the employee sees on their pay stub is only half the payroll tax picture. Employers owe additional taxes on top of gross wages that employees never see:
- Employer Social Security match: 6.2% on the same wage base ($176,100). On the $3,500/week example, the employer owes $209.92/week in SS on top of the employee deduction.
- Employer Medicare match: 1.45% on all wages, no cap. An additional $50.75/week in this example.
- FUTA (Federal Unemployment Tax Act): 6% on the first $7,000 of each employee's wages per year. Most employers receive a 5.4% credit for paying state unemployment, reducing the net FUTA rate to 0.6% — a maximum of $42 per employee per year.
- SUTA (State Unemployment Tax): Rates vary significantly by state and the employer's experience rating (claim history). New employers typically pay a higher "new employer" rate while their experience record is established. Rates in 2026 range from under 1% to over 8% depending on state and claims history.
For the $182,000/year employee in this example, the employer's incremental FICA cost alone is approximately $14,000/year. Add FUTA ($42), SUTA (varies), workers comp insurance, and benefits costs and the true cost to the employer is typically 18–25% above the stated salary.
IRS Deposit Schedules
Calculating taxes correctly is only half the job — remitting them on time is equally important. The IRS assigns each employer one of two deposit schedules based on the total tax liability reported in a lookback period (generally the 12-month period ending June 30 of the prior year):
- Monthly depositors: Must deposit all taxes withheld during a month by the 15th of the following month. New employers are automatically monthly depositors for their first calendar year.
- Semi-weekly depositors: For paydays falling on Wednesday through Friday, deposit by the following Wednesday. For paydays falling on Saturday through Tuesday, deposit by the following Friday.
- Next-day rule: If accumulated liability reaches $100,000 on any single banking day, a deposit is required the next banking day regardless of your normal schedule.
All deposits must be made via EFTPS (Electronic Federal Tax Payment System). Late deposits are penalized at rates from 2% (1–5 days late) to 15% (more than 10 days after the first IRS notice). Employers also file Form 941 quarterly to reconcile withheld taxes with deposits made.
Common Calculation Mistakes
The most frequent payroll tax errors that trigger IRS notices and state agency assessments:
- Forgetting to stop Social Security withholding once the annual wage base is reached mid-year
- Not withholding the Additional Medicare 0.9% surtax once wages exceed $200,000 in a calendar year
- Using the wrong pay period divisor when annualizing for the bracket calculation
- Treating Roth 401(k) contributions as pre-tax (they are post-tax and do not reduce federal income tax withholding)
- Failing to include bonuses and supplemental wages — these are subject to a flat 22% federal supplemental withholding rate in 2026, or they can be aggregated with regular wages if preferred
- Calculating state tax on federal taxable income rather than state taxable income (many states have different add-backs and deductions)