Updated October 1, 2026. Quick answer: The Additional Medicare Tax is 0.9% on Medicare wages, self-employment income and railroad retirement compensation above $200,000 for single and most other filers, $250,000 for married filing jointly and $125,000 for married filing separately. IRS Topic 560 states the thresholds, and an employer withholds it above $200,000 of wages.
More IRS forms and schedules for individual filers, read line by line: Schedule H Part I and Schedule H Additional Medicare Tax lines 5 and 6.
Read box by box from the IRS form text: Form W-2c boxes 1 to 20 and Form W-2c Notice to Employee.
Form lines read one part at a time: Form 8959 Part I, Form 8959 Part II and Form 8959 Part III.
Schedule 8812 (child tax credit and additional child tax credit) for 2025, read line by line: Schedule 8812 lines 21 to 26.
Schedule C and Schedule SE (Form 1040) for 2025, read line by line: Schedule SE lines 5 to 13.
Related reading on this site: Form 8959 Additional Medicare Tax.
Schedule 2 (Form 1040) for 2025, read line by line: Schedule 2 line 4, Schedule 2 lines 10 and 11 and Schedule 2 lines 19 to 21.
The employee copy of Form W-2, read box by box: W-2 boxes 10 to 20 and W-2 box 13 third-party sick pay.
The employee copy of Form W-2, read box by box: W-2 boxes 1 to 8, W-2 box 5 and W-2 box 6.
The IRS form or worksheet behind this, read line by line: Form 8960 instructions.
The thresholds
| Filing status | Threshold |
|---|---|
| Married filing jointly | $250,000 |
| Married filing separately | $125,000 |
| All other taxpayers | $200,000 |
IRS Topic 560 says “A 0.9% Additional Medicare tax applies to Medicare wages, self-employment income, and railroad retirement (RRTA) compensation that exceed the following threshold amounts based on filing status”.
Whose income counts
The IRS question-and-answer page says an individual is liable if their income, “together with that of his or her spouse if filing a joint return”, is over the threshold, and that “Medicare wages and self-employment income are combined to determine if income exceeds the threshold.” It lists head of household and qualifying widow(er) with a dependent child at $200,000, the same as single.
How employers withhold it
The IRS says “An employer is responsible for withholding the Additional Medicare tax from wages or railroad retirement (RRTA) compensation it pays to an employee in excess of $200,000 in a calendar year, without regard to filing status.” It adds “There’s no employer match for Additional Medicare tax.” That means a joint couple whose wages are each under $200,000 may owe the tax on their joint return without any withholding having taken place.
A worked example
A single filer with $230,000 of Medicare wages, an illustration and not a source figure, owes 0.9% on the $30,000 above the threshold, which is $270 (computed). The employer begins withholding in the pay period when the year’s wages pass $200,000. The reconciliation happens on a tax form: the IRS says to “Use Form 8959, Additional Medicare Tax to compute this tax”.
Common mistakes
- Assuming withholding covers a married couple. Employers withhold only above $200,000 of one employee’s wages.
- Confusing it with the net investment income tax, which applies to investment income.
- Using the joint threshold for a separate return. Married filing separately uses $125,000.
Related: the investment income counterpart, the NIIT, the Medicare and IRMAA guides, and the 2026 retirement numbers hub.
Sources
- IRS Tax Topic 560, Additional Medicare tax: https://www.irs.gov/taxtopics/tc560
- 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
Sources: the primary documents linked above, read on October 1, 2026. General information, not tax advice. Your own facts decide the outcome, and a preparer, the plan administrator or the agency itself is the right place to confirm anything consequential.