The additional Medicare tax rules affect millions of higher‑income taxpayers each year, especially dual‑income households and self‑employed professionals. Introduced under the Affordable Care Act (ACA), the Additional Medicare Tax adds 0.9% on top of the standard Medicare tax once income exceeds IRS thresholds. Because these thresholds are not indexed for inflation, more taxpayers fall under these rules annually, making it essential to understand how the tax works and how to plan for it.
This guide breaks down the additional Medicare tax rules, including thresholds, calculations, employer withholding, and strategies to manage your liability.
What Is the Additional Medicare Tax?
The Additional Medicare Tax is a 0.9% surtax applied to wages, self‑employment income, and certain railroad retirement compensation. It is separate from the standard Medicare tax:
- Employees pay 1.45% Medicare tax.
- Employers pay 1.45%.
- Self‑employed individuals pay 2.9%.
Once income exceeds the threshold, the taxpayer pays an additional 0.9%, bringing the total rate to:
- 2.35% for employees
- 3.8% for self‑employed individuals
Under the additional Medicare tax rules, only the taxpayer—not the employer—pays the extra 0.9%.
Who Must Pay the Additional Medicare Tax?
The additional Medicare tax rules apply only to taxpayers whose income exceeds IRS‑defined thresholds. These thresholds vary by filing status:
Income Thresholds
| Filing Status | Threshold |
|---|---|
| Married filing jointly | $250,000 |
| Married filing separately | $125,000 |
| Single | $200,000 |
| Head of household | $200,000 |
| Qualifying widow(er) | $200,000 |
The tax applies only to income above these limits.
Income Types Covered
The Additional Medicare Tax applies to:
- Wages subject to Medicare tax
- Self‑employment income
- RRTA compensation
There are no special exceptions for nonresident aliens or U.S. citizens abroad.
How the Additional Medicare Tax Is Calculated
Under the additional Medicare tax rules, the tax applies only to income above your filing‑status threshold.
Calculation Steps
- Add up all Medicare‑taxable income.
- Identify your filing status threshold.
- Subtract the threshold from your income.
- Apply the 0.9% rate to the excess.
Example: Single Filer
- Income: $240,000
- Threshold: $200,000
- Excess: $40,000
- Additional Medicare Tax:
The taxpayer owes $360.
Self‑Employment Rules
Self‑employed individuals calculate the tax on net earnings above the threshold, reduced by any Medicare‑taxable wages. Losses cannot reduce the threshold.
Employer Withholding Requirements
Employers must begin withholding the Additional Medicare Tax once an employee’s wages exceed $200,000, regardless of filing status. This is one of the most misunderstood additional Medicare tax rules, because:
- A married employee earning $210,000 will have withholding even if the couple’s joint income is below $250,000.
- Employers do not match the 0.9%.
- Withholding continues for the rest of the year once triggered.
If too much is withheld, the taxpayer receives a credit when filing.
Interaction With Other Taxes
The Additional Medicare Tax is separate from the Net Investment Income Tax (NIIT). NIIT applies to investment income, while the Additional Medicare Tax applies to earned income. You cannot owe NIIT on income already subject to the Additional Medicare Tax.
Reporting and Paying the Tax
Taxpayers report the Additional Medicare Tax using:
- Form 8959, Additional Medicare Tax
- Form 1040, 1040‑SR, or 1040‑NR
If your employer did not withhold enough, you may need to adjust your Form W‑4 or make estimated payments.
Strategies to Manage Additional Medicare Tax Liability
Even though you cannot avoid the tax if your income exceeds the threshold, you can reduce the amount of income subject to it.
1. Increase Pre‑Tax Contributions
Contributing to:
- HSAs
- FSAs
- Traditional retirement accounts
reduces Medicare‑taxable wages.
2. Time Self‑Employment Income
Managing income and deductions can help keep you below the threshold.
3. Adjust Withholding
Request additional withholding to avoid underpayment penalties.
Key Takeaway
The additional Medicare tax rules impose a 0.9% surtax on high‑income wages and self‑employment income. Understanding these rules helps you avoid surprises, plan withholding, and use tax‑advantaged accounts strategically. As thresholds remain fixed, more taxpayers will continue to be affected, making proactive planning essential.
This article provides information only and should not be construed as advice. It is provided without warranty of any kind.