Every paycheck shows two deductions that employees often overlook: Social Security and Medicare taxes. Together these make up FICA — the Federal Insurance Contributions Act taxes. They fund two of the largest federal programs and are entirely separate from federal income tax.
The FICA Breakdown
FICA consists of two components:
| Tax | Employee Rate | Employer Rate | Combined Rate |
|---|---|---|---|
| Social Security (OASDI) | 6.2% | 6.2% | 12.4% |
| Medicare (HI) | 1.45% | 1.45% | 2.9% |
| Total FICA | 7.65% | 7.65% | 15.3% |
As a W-2 employee, you see only the employee’s half on your paystub. Your employer pays an equal amount that never appears in your take-home pay calculation — it is an additional cost borne entirely by the employer on top of your wages.
The Social Security Wage Base
The Social Security tax has an annual earnings cap called the wage base. In 2025, the wage base is $176,100. Once your cumulative wages for the year exceed this amount, Social Security withholding stops for the remainder of the year.
This means:
- On wages up to $176,100: you pay 6.2% Social Security tax
- On wages above $176,100: no more Social Security tax
Medicare has no wage base cap — the 1.45% applies to all wages regardless of amount.
Why the Cap Matters
For a W-2 employee earning $200,000 in 2025:
- Social Security tax: $176,100 × 6.2% = $10,918.20 (then stops)
- Medicare tax: $200,000 × 1.45% = $2,900.00
- Basic FICA total: $13,818.20
For a W-2 employee earning $80,000:
- Social Security: $80,000 × 6.2% = $4,960.00
- Medicare: $80,000 × 1.45% = $1,160.00
- FICA total: $6,120.00 (7.65% of wages)
The Additional Medicare Tax
The Affordable Care Act introduced an additional 0.9% Medicare surtax on high earners starting in 2013. This tax applies to wages (and net self-employment income) above the following thresholds:
| Filing Status | Threshold |
|---|---|
| Single | $200,000 |
| Married Filing Jointly | $250,000 |
| Married Filing Separately | $125,000 |
| Head of Household | $200,000 |
Important: Your employer is only required to withhold the Additional Medicare Tax once your wages from that employer exceed $200,000 — regardless of filing status. If you are married filing jointly and your combined household wages exceed $250,000, the full liability may not be withheld. You may need to cover the shortfall via estimated tax payments or adjust your W-4 withholding.
Effective Medicare Rates With the Surtax
| Income Level | Medicare Rate |
|---|---|
| Under $200,000 | 1.45% |
| $200,001 – $250,000 (single) | 2.35% (1.45% + 0.9%) |
| Over $200,000 (single) | 2.35% on the excess |
Full FICA Example: $225,000 W-2 Wage (Single Filer)
| Component | Rate | Wages Subject | Tax |
|---|---|---|---|
| Social Security | 6.2% | $176,100 | $10,918.20 |
| Medicare (base) | 1.45% | $225,000 | $3,262.50 |
| Additional Medicare | 0.9% | $25,000 ($225k − $200k) | $225.00 |
| Total FICA | $14,405.70 |
Effective FICA rate as a percentage of gross wages: $14,405.70 ÷ $225,000 = 6.4%
Multiple Employers and the Wage Base
If you work for two employers during the year and your combined wages exceed $176,100, each employer withholds Social Security independently — potentially over-withholding. Each employer starts over at $0 for Social Security purposes.
You can claim the excess Social Security withholding as a tax credit on Form 1040. This is a credit against income tax owed (or a refund if there is no offsetting liability), not just a deduction.
For example: If Employer A pays you $120,000 and Employer B pays you $80,000, each withholds up to their own $176,100 cap. Employer A withholds $120,000 × 6.2% = $7,440. Employer B withholds $80,000 × 6.2% = $4,960. Combined: $12,400. But the maximum Social Security tax for a single employee in 2025 is $176,100 × 6.2% = $10,918.20. The excess of $12,400 − $10,918.20 = $1,481.80 is refundable via Form 1040.
FICA vs. Federal Income Tax: Key Differences
| Feature | FICA | Federal Income Tax |
|---|---|---|
| Rate | Fixed percentages | Progressive brackets (10%–37%) |
| Applies to | Wages and self-employment | Adjusted gross income |
| Wage base cap | Yes (Social Security only) | No cap |
| Standard deduction impact | None — FICA on gross wages | Reduces taxable income |
| 401(k) contributions reduce | No — FICA on pre-deferral wages | Yes — reduces taxable income |
| Purpose | Funds SS and Medicare programs | General government operations |
A critical point: 401(k) contributions do not reduce FICA. Even if you contribute $23,500 to a 401(k), FICA is still withheld on your full wage amount. This differs from income tax, where traditional 401(k) contributions lower your taxable income.
Self-Employed Workers: The SE Tax Connection
Self-employed individuals pay both halves of FICA through self-employment (SE) tax at 15.3% — the same combined rate. However, there is a key difference: SE tax is calculated on 92.35% of net self-employment income (to approximate the fact that employees pay FICA on wages that already exclude the employer’s share).
Additionally, self-employed workers can deduct half of SE tax as an above-the-line deduction on Form 1040, partially offsetting the higher burden of paying both sides.
Tips for Managing FICA
If you expect Additional Medicare Tax: Review withholding mid-year. File Form W-4 to request additional withholding, or make an estimated tax payment in Q3 or Q4.
If you have multiple jobs: Track cumulative wages across employers. If total wages will exceed $176,100, you may want to hold one employer responsible for excess Social Security withholding. Alternatively, file your return knowing a credit is coming.
If you are near the wage base: In years where you expect to exceed $176,100, cash flow improves later in the year when Social Security withholding stops. Factor this into cash flow planning.
Key Takeaways
- FICA consists of 6.2% Social Security + 1.45% Medicare = 7.65% employee share on every paycheck.
- The Social Security wage base for 2025 is $176,100; no more SS tax is withheld after that.
- Medicare has no cap — but an additional 0.9% surtax applies above $200,000 for single filers.
- Your employer matches your 7.65% contribution but you never see that cost on your paystub.
- 401(k) contributions do not reduce FICA — only income tax.
- Multiple employer over-withholding of Social Security is refunded via Form 1040.