Additional Medicare Tax for Self-Employed Individuals

Self-employed individuals pay additional Medicare tax—a 0.9% surtax—on net self-employment earnings above a threshold ($200,000 single, $250,000 married). Unlike the base 2.9% Medicare portion of self-employment tax, which applies to all net earnings regardless of income level, the additional 0.9% is an income-tested surtax enacted under the Affordable Care Act. It stacks on top of the regular Medicare tax and applies only when earnings exceed the high-income threshold.

The Two-Layer Medicare Tax System

Self-employed individuals have long paid self-employment tax—essentially Social Security and Medicare taxes that employees would split with an employer. The rate is 15.3%: 12.4% for Social Security (on earnings up to a cap) and 2.9% for Medicare (unlimited earnings).

In 2013, the additional Medicare tax added a second layer. Above the high-income threshold, an extra 0.9% Medicare tax applies. This is separate from—and stacks on top of—the base 2.9%.

For a high-earning self-employed person, the total Medicare tax is therefore:

• 2.9% on all net self-employment earnings (up to the earnings cap for Social Security), plus
• 0.9% on earnings above the threshold ($200,000 single)

So at high enough earnings, the Medicare portion becomes 3.8% instead of 2.9%.

Calculating the Tax Base

The additional Medicare tax applies to net self-employment earnings, not gross revenue.

Net self-employment earnings is the Schedule C or Schedule F net profit (or net loss) reduced by half the self-employment tax itself. It’s not based on gross income, salary, or dividends; it’s the net income from self-employment activities.

Here’s the basic flow:

1. Calculate net profit on Schedule C (business income minus ordinary business expenses) or Schedule F (farm income).
2. Reduce by half of self-employment tax (this accounts for the deductible portion of SE tax).
3. Apply the threshold: additional Medicare tax applies to the excess over $200,000 (single) or $250,000 (married).

Worked Example

Single self-employed consultant, 2024:

• Gross business income: $350,000
• Business expenses: $50,000
• Net profit on Schedule C: $300,000

Self-employment tax calculation:

• Net earnings for SE tax: $300,000 × 0.9235 (adjustment factor) = $277,050
• Base SE tax (15.3%): $277,050 × 0.153 = $42,398.65
• Half of SE tax (deductible): $21,199.33

Income subject to additional Medicare tax:

• Net profit: $300,000
• Less: half of SE tax: −$21,199.33
• Adjusted net earnings: $278,800.67

Additional Medicare tax calculation:

• Threshold: $200,000
• Excess earnings: $278,800.67 − $200,000 = $78,800.67
• Additional Medicare tax: $78,800.67 × 0.9% = $709.21

This $709.21 is in addition to the regular $42,398.65 self-employment tax, for a total Medicare-related tax of approximately $43,107.86.

The Threshold Is Not Indexed

The $200,000 (single) and $250,000 (married filing jointly) thresholds are fixed—they do not adjust annually for inflation, unlike most income tax brackets. This is politically significant: over time, as real income grows with inflation, more and more middle-to-high-income self-employed individuals will cross the threshold.

A consultant earning $200,000 in 2013 is spared the additional Medicare tax. A consultant earning the same inflation-adjusted amount in 2026 may not be.

Married filing separately filers face a $125,000 threshold—half the joint threshold. This creates a significant marriage penalty for dual-income self-employed couples.

The Distinction from Regular Self-Employment Tax

A common confusion: is the additional Medicare tax the same as the regular Medicare portion of self-employment tax?

No. Here’s the distinction:

A self-employed person earning $100,000 pays 2.9% Medicare tax on that $100,000 (no additional tax).

A self-employed person earning $250,000 pays 2.9% Medicare tax on the full $250,000 ($7,250) plus 0.9% additional Medicare tax on the portion above $200,000 ($450 × 0.009 = $2,700), for a combined $9,950.

W-2 Employees vs. Self-Employed

W-2 employees and their employers split the additional Medicare tax equally:

• Employee withholds 0.45% on wages above $200,000 (single)
• Employer pays 0.45% on wages above $200,000 (single)
• Combined: 0.9%

Self-employed individuals pay the full 0.9% themselves (and can deduct half).

From an employer’s perspective, hiring an employee vs. contracting with a self-employed service provider creates a difference in Medicare tax burden. An employer would withhold the employee’s portion but also pay the employer’s portion, whereas self-employed contractors bear the full additional Medicare tax.

When Both W-2 and Self-Employment Income Apply

High-income earners often have both W-2 wages and self-employment income. The additional Medicare tax threshold applies to the sum of:

• Wages subject to Medicare withholding, plus
• Net self-employment income

If a filer has W-2 wages of $180,000 and self-employment income of $50,000:

• Total income subject to Medicare taxes: $230,000
• Single filer threshold: $200,000
• Excess: $30,000
• Additional Medicare tax: $30,000 × 0.9% = $270

The W-2 employer withholds the employee’s portion of additional Medicare tax on the wages (up to the portion of wages in excess of the threshold). Any shortfall—if self-employment income pushes the total over the threshold—is paid via estimated tax or reconciled on the return.

Reporting and Payment

Additional Medicare tax is calculated on Form 8959 and reported on the taxpayer’s Form 1040 (Schedule 2, line 8).

For self-employed filers:

• Calculate on Form 8959.
• Include in estimated quarterly tax (Form 1040-ES) or pay via withholding adjustment if you have W-2 income.
• The tax is not subject to self-employment tax adjustment but is a direct income tax.

The additional Medicare tax does not count toward the self-employment tax caps (Social Security); it applies to all net self-employment earnings above the threshold, without limitation.

Key Differences from Other High-Income Taxes

The additional Medicare tax can be confused with the net investment income tax (3.8% NIIT), which applies to passive investment income, or the alternative minimum tax, which is a separate parallel tax system.

• Additional Medicare tax: 0.9% on self-employment income (and W-2 wages) above $200,000/$250,000. Applies to active earned income.
• Net investment income tax: 3.8% on passive investment income (dividends, capital gains, rental income) above the same threshold.
• AMT: Parallel tax system based on alternative minimum taxable income; rate 26%–28%.

A high-income self-employed person could owe all three: AMT (if applicable), 0.9% additional Medicare tax on earnings, and 3.8% NIIT on passive investment income.

Planning for Self-Employed Individuals

Self-employed filers above the threshold should:

1. Estimate early: Include additional Medicare tax in quarterly estimated tax payments (Form 1040-ES). Underpayment penalties apply if too little is paid.

2. Consider entity structure: Electing S-corporation status allows a self-employed person to split net income into W-2 wages (subject to full self-employment and Medicare tax) and S-corp distributions (not subject to self-employment tax, but subject to additional Medicare tax based on income threshold). This can reduce the total SE and Medicare tax burden, though the W-2 wage floor is set by reasonableness and IRS scrutiny.

3. Maximize pre-tax deductions: SEP-IRA or Solo 401(k) contributions reduce net self-employment income and thus the base for additional Medicare tax.

4. Coordinate with other high-income taxes: High earners should review all surtaxes (additional Medicare, NIIT, AMT) together to understand total tax burden and opportunities for income timing or entity choice.

See also