Form 8959 is the IRS form for the Additional Medicare Tax, a 0.9% tax on Medicare wages, railroad retirement (RRTA) compensation and self-employment income above a threshold: $200,000 single, $250,000 married filing jointly, $125,000 married filing separately. You attach it to your Form 1040, 1040-SR, 1040-NR or 1040-SS. Those thresholds aren't indexed for inflation.
The reason it surprises people is that employers only withhold it once your wages from that one job pass $200,000. Two earners on $150,000 each can owe it with nothing withheld. Everything below comes from the IRS Instructions for Form 8959 (2025), checked in October 2026.
The thresholds
| Filing status | Threshold, as of October 2026 |
|---|---|
| Married filing jointly | $250,000 |
| Married filing separately | $125,000 |
| Single | $200,000 |
| Head of household | $200,000 |
| Qualifying surviving spouse | $200,000 |
Who must file Form 8959
- Your Medicare wages and tips on any single Form W-2 (box 5) are more than $200,000.
- Your RRTA compensation on any single Form W-2 (box 14) is more than $200,000.
- Your Medicare wages and tips plus self-employment income, combined with your spouse's on a joint return, are more than your filing status threshold.
- Your RRTA compensation, combined with your spouse's on a joint return, is more than your filing status threshold.
A self-employment loss doesn't count against the total, and RRTA compensation is compared to the threshold separately from wages and self-employment income.
How the IRS examples work it out
| Example | Income | Taxed at 0.9% |
|---|---|---|
| Ann, single | $130,000 self-employment, no wages | Nothing, and no form |
| Bob, single | $220,000 self-employment, no wages | $20,000 |
| Carl, single | $145,000 self-employment, $130,000 wages | $75,000 of self-employment income |
| Don, married filing separately | $150,000 self-employment, $200,000 wages | $75,000 of wages and $150,000 of self-employment income |
| Erin and Frank, joint | $150,000 and $175,000 wages | $75,000 of wages |
| George and Helen, joint | $190,000 wages and $150,000 RRTA compensation | Nothing, because RRTA compensation isn't added to wages |
Carl is the pattern most freelancers with a day job miss. His $130,000 of wages uses up part of the $200,000 threshold, which leaves only $70,000 for his self-employment income. His employer withheld nothing because his wages were under $200,000, but he still owes it on $75,000.
Erin and Frank show the joint-return trap: neither job crossed $200,000, so neither employer withheld, but together they're $75,000 over the $250,000 joint threshold. George and Helen are the opposite case: his $190,000 of wages and her $150,000 of RRTA compensation are each tested against the $250,000 joint threshold separately, so neither part is over and they owe nothing.
How to complete it
- Part I: Medicare wages and tips from Form W-2 box 5, plus tips from Form 4137 and wages from Form 8919 if you have them.
- Part II: self-employment income from Schedule SE, Part I, line 6, ignoring a loss.
- Part III: RRTA compensation, if you have any.
- Part IV: add up the Additional Medicare Tax from Parts I to III.
- Part V: work out how much your employer withheld. Medicare tax and Additional Medicare Tax are reported together in box 6 of Form W-2, so the form separates them for you.
- Carry the totals to your return and attach Form 8959.
If your self-employment income is the reason you owe it, your Schedule SE figures feed straight into Part II. And because employers won't withhold it below $200,000, the fix for next year is usually estimated tax payments or extra withholding.
Planning for 2026
The instructions are specific about the fix. If you expect to owe Additional Medicare Tax for 2026, you can ask your employer to withhold more income tax by giving them a new Form W-4. You can't ask for extra withholding labeled as Additional Medicare Tax: the extra simply counts against all the tax on your return. If withholding won't cover it, you may need estimated tax payments, which also can't be designated for this tax alone.
- Add up your expected wages, RRTA compensation and self-employment income for the year, and your spouse's if you file jointly.
- Compare the total with your filing status threshold.
- If you're over, multiply the excess by 0.9% to see roughly what you'll owe.
- Cover it with a new W-4 at your job or with quarterly estimated payments.
If your wages, RRTA compensation or self-employment income are later adjusted, for example by a corrected W-2, the instructions say you may need to correct your Additional Medicare Tax too, by attaching a corrected Form 8959 to your original or amended return.
What the employer does and doesn't do
Your employer must start withholding the 0.9% in the pay period your wages for the year pass $200,000, and keep withholding for the rest of the calendar year, whatever another employer pays you. They don't look at your filing status, your spouse's pay or your side income, and you can't ask them to stop if they're required to withhold. So the opposite can happen too: if one spouse earns just over $200,000 and the couple's joint total is under $250,000, tax is withheld that isn't owed. The instructions say you claim a credit for it against your total tax by filing Form 8959.
There are no special rules for nonresident aliens or U.S. citizens living abroad: if the wages or self-employment income are subject to Medicare tax, they're subject to this tax above the threshold too.
The other surtax on bigger gains is explained in our guide to the net investment tax.
Want AI doing the heavy lifting in your marketing?
I build the systems that handle the boring 80 percent, so you get your week back. Done properly, with the human kept in.
The verdict
If your household's combined wages and self-employment income are anywhere near $200,000 or $250,000, run Form 8959 even if no employer withheld it. Two-income couples and people with a salary plus a side business are the ones who end up owing, and the fix is cheap: raise your withholding or add estimated payments before the year ends.
If an employer skipped withholding, our guide to uncollected payroll tax shows the fix.
Frequently asked questions
What is Form 8959?
It's the form used to figure the 0.9% Additional Medicare Tax you owe and how much of it your employer withheld.
What is the Additional Medicare Tax threshold?
$200,000 for single, head of household and qualifying surviving spouse, $250,000 married filing jointly and $125,000 married filing separately. These amounts aren't indexed for inflation.
Why didn't my employer withhold Additional Medicare Tax?
Employers only withhold it on wages over $200,000 paid by that employer in a calendar year, whatever your filing status or other income.
Does self-employment income count toward the threshold?
Yes. Medicare wages and self-employment income are combined, and wages reduce the threshold that applies to self-employment income.
Do I combine RRTA compensation with wages?
No. RRTA compensation is compared to the threshold separately, as the IRS examples for George and Helen show.
Where do I find Additional Medicare Tax withheld on my W-2?
In box 6, where it's reported together with regular Medicare tax withheld. Form 8959 Part V separates the two.
