Additional Medicare Tax: The 0.9% Surtax Explained (2026)

This article is for general information, not tax or legal advice. The figures below are current for the 2026 tax year. The Additional Medicare Tax thresholds are set by statute and are not indexed for inflation, but always verify current rules with the IRS or a tax professional before you file.

If you earn a high salary, run payroll for someone who does, or file jointly with a working spouse, you have probably seen a line on a pay stub or a tax form labeled Additional Medicare Tax. It is 0.9%, and it trips up more people than almost any other payroll number.

The reason is a mismatch most guides skip over. The amount your employer withholds is decided by one rule, and the amount you actually owe is decided by a different rule. When those two rules disagree, you either get a surprise bill in April or a refund you did not expect. That gap is what the rest of this explains.

What is the Additional Medicare Tax (and why 0.9%)?

The Additional Medicare Tax is a 0.9% surtax on earned income above a threshold. Congress created it in the Affordable Care Act, and it took effect in 2013.

It sits on top of the regular Medicare tax. Every worker already pays 1.45% Medicare on all wages, with no cap. Once your income passes the threshold, an extra 0.9% applies to the dollars above it, so those dollars are taxed at 2.35% for Medicare.

One detail matters more than any other: this is an employee-only tax. There is no employer match. Regular Medicare is split 1.45% and 1.45% between worker and employer, but the 0.9% surtax is carried entirely by the earner. We cover the employer side of standard FICA in our employer FICA match guide.

It also applies to more than just W-2 wages. Self-employment income and Railroad Retirement (RRTA) compensation above the threshold are subject to the same 0.9%. And unlike Social Security, there is no wage ceiling. The surtax keeps applying to every dollar above the threshold, no matter how high your income climbs.

The two thresholds nobody explains: withholding vs. what you owe

This is the part that causes the confusion, so it is worth slowing down.

There are two different numbers at play, and they serve different jobs.

The withholding trigger is a flat $200,000. Your employer must start withholding the 0.9% in the pay period when your year-to-date wages with that employer cross $200,000. Your filing status does not enter into it. A married employee, a single employee, and a head-of-household employee all get 0.9% withheld starting at the same $200,000 mark.

The liability threshold, though, depends on your filing status. What you actually owe is figured on your tax return using your household income against a threshold that changes by filing status: $250,000 married filing jointly, $125,000 married filing separately, and $200,000 for everyone else.

Because your employer only knows your wages, not your spouse’s income or your filing status, the withholding is a rough estimate. The tax return is where the real number gets settled. When the estimate and the real number do not match, you reconcile the difference on Form 8959.

Two common outcomes fall out of this gap. A single earner who never crosses $200,000 for the year but gets 0.9% withheld on a one-time bonus has too much withheld, and gets it back. A dual-earner couple where each spouse stays under $200,000 individually, but who together clear $250,000, has nothing withheld at source and owes the full amount in April.

Who pays it: thresholds by filing status (2026)

The thresholds have not moved since 2013, and they do not adjust for inflation, so the 2026 numbers are the same figures that applied when the tax began.

| Filing status | Liability threshold (2026) | |---|---| | Single | $200,000 | | Head of household | $200,000 | | Married filing jointly | $250,000 | | Married filing separately | $125,000 |

Compare that to the employer withholding trigger, which is a flat $200,000 for every employee regardless of the column they fall into. Notice that married filing jointly is $250,000, not double the single amount, and married filing separately is only $125,000, the lowest of the group.

Because the thresholds are frozen, more people drift into paying this tax each year as wages rise. That is different from Social Security, whose 2026 wage base of $184,500 climbs most years with the cost of living.

How to calculate it: worked examples

The math itself is simple: 0.9% times the income above your threshold. The work is in figuring out which income counts and which threshold applies.

Example 1: single filer, $230,000 in wages

Single threshold is $200,000. Income above it is $30,000.

Additional Medicare Tax: $30,000 × 0.9% = $270

The employer would have withheld this automatically, since the wages crossed $200,000, so at filing this taxpayer likely comes out even.

Example 2: dual-earner couple, married filing jointly

One spouse earns $150,000, the other earns $175,000, for a combined $325,000. Their joint threshold is $250,000, so $75,000 is over.

Additional Medicare Tax: $75,000 × 0.9% = $675

Here is the trap. Neither spouse individually crossed $200,000, so neither employer withheld a cent of the surtax. The full $675 lands as a balance due on the tax return. This is the classic dual-earner surprise, and it matches the IRS’s own example of a couple who each earn well under $200,000 but owe on their combined income.

Example 3: self-employed with wages

Say you earn $180,000 in W-2 wages and $90,000 in net self-employment income, filing single. The $200,000 threshold applies to your combined earnings, but the rules take your wages into account first.

Your wages use up $180,000 of the $200,000 threshold, leaving only $20,000 of threshold for the self-employment income. So $90,000 minus $20,000 = $70,000 of self-employment income is subject to the surtax.

Additional Medicare Tax on SE income: $70,000 × 0.9% = $630

Above the threshold, self-employment income carries a 3.8% Medicare rate: the regular 2.9% self-employment Medicare tax plus the 0.9% surtax. Wages above the threshold, by contrast, hit the 2.35% employee rate.

Form 8959: reporting, reconciliation, and refunds

Form 8959 is where all of this gets settled, and you file it with your Form 1040.

The form has five parts. They walk through your Medicare wages, your self-employment income, and your RRTA compensation, apply the right filing-status threshold to each, and total the 0.9% you owe.

The last part is the reconciliation. It compares the Additional Medicare Tax your employer actually withheld, which shows up as part of the Medicare tax in box 6 of your W-2, against what you truly owe. Any amount your employer withheld beyond the regular 1.45% is credited toward your final bill.

If your employer withheld more than you owe, the excess flows back to you as additional federal income tax withholding, which raises your refund or lowers your balance. If they withheld less than you owe, the shortfall is added to your tax bill. Either way, the form is what turns the flat $200,000 withholding rule into your correct filing-status liability.

What employers and payroll runners must do

If you run payroll, your obligations here are narrow but strict.

Start withholding the 0.9% in the pay period when an employee’s year-to-date Medicare wages with you cross $200,000. Keep withholding it on every dollar after that through year-end. You do not ask about filing status, and you do not stop just because the employee tells you their spouse’s income will keep them under the joint threshold.

Worth repeating: there is no employer match on the 0.9%. You withhold it and remit it, but the business pays nothing extra. Treating it as a matched tax like regular Medicare is a common and costly bookkeeping error.

You also cannot net it across employees. Each person’s $200,000 trigger is based only on their own year-to-date wages with your business, so the surtax has to be tracked per employee, on the exact dollar where they cross the line. That per-person, year-to-date tracking is the same discipline the Social Security wage base demands, and it is exactly what WorkLogs44 handles when you run a whole team at once, computing each person’s withholding independently and decimal-precise. You can run your own numbers with the calculator tools or browse more payroll guides if you want to go deeper.

Frequently Asked Questions

What is the Additional Medicare Tax and why is it 0.9%?

The Additional Medicare Tax is a 0.9% surtax on wages, self-employment income, and RRTA compensation above a set threshold. It was created by the Affordable Care Act and took effect in 2013. It stacks on the regular 1.45% Medicare tax, so employee wages above the threshold are taxed at 2.35% for Medicare.

Who has to pay the 0.9% Additional Medicare Tax in 2026?

Individuals whose Medicare wages or self-employment income exceed their filing-status threshold pay it. The thresholds are $200,000 for single and head of household filers, $250,000 for married filing jointly, and $125,000 for married filing separately. It is an employee-only tax with no employer match.

Why did my employer withhold the Additional Medicare Tax when I earn under $250,000?

Employers must start withholding the 0.9% once your individual year-to-date wages with them cross $200,000, and they ignore filing status when doing so. If your household threshold is actually $250,000, you may get the over-withheld amount back when you file Form 8959 with your return.

Does my employer match the 0.9% Additional Medicare Tax?

No. The 0.9% is the employee’s tax alone. The employer must withhold and remit it once your wages cross $200,000, but the business does not pay a matching 0.9%. This is different from regular Medicare, which the employer matches at 1.45%.

Does the Additional Medicare Tax apply to self-employment income?

Yes. Net self-employment income above your filing-status threshold is subject to the 0.9%. Combined with the 2.9% self-employment Medicare rate, income above the threshold is taxed at 3.8% for Medicare. Wages you also earn reduce the threshold available for your self-employment income.

Why do I owe more, or get a refund, at tax time even though something was withheld?

Withholding is based on a flat $200,000 per employer, while your actual liability is figured on your household income against your filing-status threshold. Dual-earner couples often owe more because neither employer withheld enough. Single earners who had 0.9% withheld on a bonus but never truly crossed the threshold get the excess back.

Want to see the surtax, the FICA match, and take-home pay for your whole team in one place? Get WorkLogs44 and run every employee’s numbers at once.