When you inspect your pay stub, you will notice mandatory deductions labeled FICA, OASDI, Social Security, or Medicare. Unlike federal income tax withholding—which is an estimated advance on your annual income tax return—FICA deductions are dedicated payroll taxes that directly fund the nation’s two largest social safety nets: Social Security and Medicare.
Under the Federal Insurance Contributions Act (FICA), both employees and employers are legally required to contribute a percentage of earned wages to these trust funds.
1. The Components of FICA Tax
FICA is made up of two distinct taxes with different rates and wage limits:
| Tax Component | Official Program Name | Employee Rate | Employer Match | 2026 Annual Wage Limit |
|---|---|---|---|---|
| Social Security | Old-Age, Survivors, and Disability Insurance (OASDI) | 6.2% | 6.2% | $181,800 (Annual statutory cap) |
| Medicare | Hospital Insurance (HI) | 1.45% | 1.45% | No Limit (Applies to all earnings) |
| Additional Medicare | Affordable Care Act Provision | 0.9% | None (Employee only) | Over $200,000 threshold |
In total, standard W-2 employees pay 7.65% of their gross wages toward FICA (up to the Social Security cap), matched by an identical 7.65% paid directly by their employer.
2. Social Security Tax (OASDI) and the Annual Wage Base
The Social Security portion of FICA is 6.2%. However, unlike income tax, Social Security is not levied on unlimited earnings. Congress established an annual maximum taxable wage base that adjusts each year with national average wage indexing.
- For tax year 2026, the Social Security wage base limit is $181,800.
- The maximum Social Security tax an employee can pay in 2026 is:
$181,800 × 6.2% = $11,271.60
Once your cumulative year-to-date (YTD) earnings from an employer pass $181,800, your employer must immediately stop withholding the 6.2% Social Security tax for the remainder of that calendar year. On the following January 1, the wage counter resets to zero.
3. Medicare Tax (HI) and Additional Medicare Withholding
The Medicare portion of FICA is 1.45%. Unlike Social Security, Medicare has no wage cap. Every dollar of earned income—whether $30,000 or $3,000,000—is subject to the 1.45% Medicare tax.
The 0.9% Additional Medicare Tax
Under the Affordable Care Act, high earners are subject to an Additional Medicare Tax of 0.9% (bringing the total employee Medicare rate to 2.35% on earnings over statutory thresholds).
Crucial Employer Withholding Rule: Under IRS rules in Publication 15, an employer must begin withholding the 0.9% Additional Medicare tax in the pay period in which wages paid to an employee exceed $200,000 in a calendar year, regardless of the employee’s marital status or Form W-4 filing status.
When you file your annual tax return (Form 1040), the actual threshold depends on your filing status ($250,000 for Married Filing Jointly, $125,000 for Married Filing Separately, and $200,000 for Single). Any difference between employer withholding and your final liability is reconciled on Form 8959.
4. Which Deductions Reduce FICA Taxable Wages?
Not all payroll deductions reduce your FICA tax base. In fact, one of the most critical rules in payroll accounting is:
- Traditional 401(k), 403(b), and Traditional IRA: DO NOT reduce FICA taxable wages. Even if you contribute $23,500 to a 401(k), you still pay Social Security and Medicare taxes on that entire amount.
- Section 125 Cafeteria Plans: DO reduce FICA taxable wages. Pre-tax contributions toward employer health insurance, dental/vision premiums, Health Savings Accounts (HSA), and Healthcare/Dependent Care Flexible Spending Accounts (FSA) are statutory pre-tax deductions that completely bypass FICA.
Comparison Table: Deduction Impact on FICA
| Payroll Deduction | Reduces Federal Income Tax? | Reduces FICA Payroll Tax? |
|---|---|---|
| Traditional 401(k) / 403(b) | Yes | No |
| Roth 401(k) | No | No |
| Employer Health Insurance (Sec 125) | Yes | Yes |
| Health Savings Account (HSA via Payroll) | Yes | Yes |
| Flexible Spending Account (FSA) | Yes | Yes |
| Post-Tax Wage Garnishments | No | No |
5. Worked Example: FICA on a $100,000 Salary
Let us examine the exact FICA deductions on a $100,000 annual salary paid biweekly (26 pay periods) with $150 per check in Section 125 health insurance:
- Gross Pay per Paycheck:
$3,846.15 - Section 125 Health Deduction:
-$150.00 - FICA Taxable Wages:
$3,696.15
Paycheck FICA Line Items:
- Social Security (6.2%):
$3,696.15 × 0.062 = $229.16 - Medicare (1.45%):
$3,696.15 × 0.0145 = $53.59 - Additional Medicare:
$0.00(Annual wages under $200k threshold) - Total FICA Deductions per Paycheck:
$282.75(Annualized:$7,351.50)
To see how FICA interacts with your federal and state tax withholding, run your scenario on our Paycheck Calculator.
Official Sourcing & References
- Social Security Administration (SSA) 2026 Fact Sheet: https://www.ssa.gov/cola/factsheets/2026.html
- IRS Publication 15 (Circular E, Employer’s Tax Guide): https://www.irs.gov/publications/p15
- IRS Questions and Answers for the Additional Medicare Tax: https://www.irs.gov/businesses/small-businesses-self-employed/questions-and-answers-for-the-additional-medicare-tax