Additional Medicare Tax Calculator
Work out the 0.9% Additional Medicare Tax for your filing status, compare it with what your employer withheld above $200,000, and see the Form 8959 gap.
Additional Medicare Tax Calculator
Filing status and wages
Qualifying surviving spouse uses the same $200,000 threshold as single.
Box 5, not box 1. Medicare wages are figured before 401(k) deferrals but after Section 125 benefits.
Withholding is tested per employer. With two jobs, enter the larger one: neither employer counts the other's wages.
Self-employment and railroad income
Net earnings after the 92.35% factor. A loss counts as zero and never offsets wages.
Tested against the full threshold on its own. It never pools with wages.
Unreported tips (Form 4137) and Form 8919 wages also feed Form 8959 line 1 and are out of scope here.
Pay frequency
Drives the per-paycheck view only. It does not change what you owe for the year.
Try an example
Four cases where withholding and liability part ways.
Employer withholding starts on the first dollar above $200,000 with that employer, regardless of your filing status.
Medicare and the 0.9% surtax have no wage ceiling, unlike Social Security, which stops at the 2026 wage base of $184,500.
How the 0.9% Additional Medicare Tax works
The Additional Medicare Tax is a flat 0.9% on earned income above a threshold set by your filing status. It arrived with the Affordable Care Act, and it only touches earned income: wages, tips, self-employment income, and RRTA compensation. Investment income is outside it, covered instead by the separate 3.8% net investment income tax.
The 2026 thresholds are the same statutory figures used every year since the tax began:
- Single: $200,000
- Married filing jointly: $250,000
- Married filing separately: $125,000
- Head of household: $200,000
- Qualifying surviving spouse: $200,000
None of these are indexed for inflation, so more workers cross them every year. Above the threshold your marginal Medicare rate on wages is 2.35% (1.45% base plus 0.9%), with no employer match on the surtax portion. Medicare also has no wage ceiling, which catches people out: Social Security stops at the 2026 wage base of $184,500, but Medicare and the surtax keep going on every dollar.
Worked through: a single filer earning $240,000 has $40,000 above the threshold, so the surtax is 0.9% of $40,000, or $360. Total Medicare tax on those wages is $3,480 plus $360, which is $3,840, an effective rate of 1.60%.
Employer withholding at $200,000 vs. what you actually owe
Two rules run in parallel here, and the gap between them is why people get surprised in April. Under IRC 3102(f), every employer has to start withholding the 0.9% once it pays a single employee more than $200,000 in a calendar year. That rule ignores your filing status, your spouse, and any other job. Form 8959 then works out your real liability by testing household earned income against your filing-status threshold.
The classic under-withheld case: two spouses earn $180,000 each. Neither employer crosses $200,000, so nothing is withheld. Combined wages are $360,000, which is $110,000 above the $250,000 joint threshold, so the return owes $990 that nobody set aside.
It runs the other way too. Take a single-earner joint household with $260,000 from one employer. That employer withholds 0.9% of $60,000, or $540. Actual liability is 0.9% of the $10,000 above $250,000, or $90. The extra $450 was over-withheld, and it gets credited against total tax on the return, refundable if it exceeds the bill.
Wages, self-employment income, and RRTA: the order the IRS applies them
Form 8959 runs three income types through three parts, and the order matters. Part I tests Medicare wages against the full threshold. Part II handles self-employment income, but first it reduces the threshold by the wages already tested, never below zero. Part III treats RRTA compensation on its own against the full threshold, with no pooling and no reduction.
The IRS uses this example: a single filer with $130,000 of wages and $145,000 of self-employment income. Wages are below $200,000, so Part I produces nothing. The threshold for Part II drops to $70,000 ($200,000 minus $130,000), which leaves $75,000 of SE income subject to the surtax, or $675. Add the two income figures together first and you get a different, wrong answer. A self-employment loss clamps to zero and never offsets wages.
Fixing a shortfall before you file
You cannot ask an employer to withhold the Additional Medicare Tax specifically; the trigger is statutory. What you can do is add extra income tax withholding on Form W-4 Step 4(c), or send quarterly estimated payments. Both go against your total liability, and this tax is part of that total, so either one closes the gap. Checking in mid-year, around the time a bonus or a second job pushes you over, is usually enough to stay clear of an underpayment penalty.
On the payroll side, employers report wages subject to Additional Medicare Tax withholding on Form 941 line 5d, and the surtax is employee-only in the deposit, with no employer share to match. If you run payroll and have to watch year-to-date wages against the $200,000 trigger for a whole team, the Payroll Calculator app does multi-employee payroll and keeps the YTD figures to the cent.
Frequently Asked Questions
Common questions about additional medicare tax calculator
When does the 0.9% Additional Medicare Tax start?
It applies to the first dollar of earned income above your filing-status threshold: $200,000 for single and head of household, $250,000 married filing jointly, and $125,000 married filing separately. Congress wrote those numbers into the statute and never indexed them for inflation, so 2026 uses the same figures as the first year of the tax.
Does my employer withhold the Additional Medicare Tax automatically?
Yes, but only once that one employer pays you more than $200,000 in a calendar year. The employer rule ignores your filing status, your spouse's income, and any other job you hold. So the withholding rule and the liability rule can disagree, and the headline number on this page is that difference.
What income triggers the Additional Medicare Tax?
Earned income only: Medicare wages, tips, self-employment income, and RRTA compensation. Investment income is not part of it. That gets taxed separately under the 3.8% net investment income tax, which confusingly uses similar-looking thresholds.
Why do I owe Additional Medicare Tax when nothing was withheld?
Employers test each job against $200,000, while the IRS tests your household earned income against your filing-status threshold. Two spouses earning $180,000 each trigger no withholding at either employer, yet the joint return owes $990 (0.9% of the $110,000 above $250,000). Load the "MFJ trap" example above to watch it happen.
Does my employer match the 0.9% Additional Medicare Tax?
No. The 1.45% base Medicare tax is matched; the 0.9% surtax is not, so the employee pays all of it. Employers still have to report what they withheld, which is why it turns up on line 5d of the Form 941 quarterly payroll tax return.
What's the threshold if I'm married filing separately?
It is $125,000, the lowest of any filing status. An MFS filer earning $150,000 owes $225 of Additional Medicare Tax with nothing withheld, because the employer trigger stays at $200,000 no matter which status you file.
How does self-employment income change the calculation?
Your wages reduce the threshold applied to self-employment income, though never below zero, so you cannot just add the two together. Take the IRS example: a single filer with $130,000 of wages and $145,000 of self-employment income has the threshold cut to $70,000, leaving $75,000 of SE income subject to the surtax. For the bigger picture on contract income, there is the 1099 vs W-2 take-home calculator.
How do I fix an under-withholding shortfall before filing?
You cannot ask an employer to withhold the surtax specifically. What you can do is add extra income tax withholding on Form W-4 Step 4(c), or make estimated tax payments. Both apply against your total liability, and this tax is part of that total. The W-4 paycheck withholding calculator turns a shortfall into a per-paycheck Step 4(c) figure.