Open your pay stub and find the Medicare line. For most of residency it reads 1.45 percent of gross, and you never think about it again. Then attending income arrives, and somewhere past $200,000 of year-to-date wages a second line appears: another 0.9 percent, employee-only, with no and no wage ceiling. The Additional Medicare Tax is small enough to overlook and structured strangely enough to hand physician households a surprise balance due that nobody withheld for. This article walks through where the 0.9 percent comes from, why its thresholds never move, why the withholding rules are mathematically guaranteed to miss for two-attending couples and multi-employer physicians, and how Form 8959 settles the difference every April.
Medicare tax has no ceiling, and above $200,000 it grows a second tier
Standard FICA has two components, and they behave differently at attending income. The Social Security portion is 6.2 percent from you and 6.2 percent from your employer, but it stops at the annual wage base: $184,500 for 2026 (IRS Topic 751). Once your year-to-date wages cross that line — which happens by early autumn for many attendings — the Social Security line on your stub goes quiet.
The Medicare portion never stops. It is 1.45 percent from you and 1.45 percent from your employer on every dollar of Medicare wages, with no wage base limit. On top of that base rate, Internal Revenue Code section 3101(b)(2), added by the Affordable Care Act and effective for tax years beginning after December 31, 2012, imposes the Additional Medicare Tax: 0.9 percent on Medicare wages above a threshold that depends on your filing status.
| Filing status | Additional Medicare Tax threshold |
|---|---|
| Married filing jointly | $250,000 |
| Married filing separately | $125,000 |
| Single | $200,000 |
| Head of household | $200,000 |
| Qualifying surviving spouse | $200,000 |
Three structural details matter. First, the 0.9 percent is employee-only — there is no employer match, which is why it lives on your stub but not in your employer's payroll budget. Second, it applies to Medicare wages, which include call pay, quality bonuses, and reconciliations, not just base salary — if you want the full anatomy of those lines, start with the paycheck-decoded module. Third, it stacks on top of your ordinary income tax brackets rather than appearing in them, which is why the tax-brackets module calls this family of surtaxes the shadow schedule: real increases that never show up in the published bracket table.
Congress froze the thresholds in 2013, and inflation recruits new payers every year
Nearly every dollar figure in the tax code moves each year. Brackets, the standard deduction, and retirement limits are all indexed and republished annually (for 2026, in Rev. Proc. 2025-32). The Additional Medicare Tax thresholds are the exception: the Form 8959 instructions state flatly that the threshold amounts are not indexed for inflation. The $200,000 and $250,000 lines are the same numbers Congress wrote for 2013, and there is no mechanism in the statute to update them.
That freeze is the stealth-bracket mechanic. A threshold that sat comfortably above most physician starting offers in 2013 now sits at or below typical first-year attending compensation in many specialties, and every year of ordinary wage inflation pulls more physicians — and more of each physician's income — across a line that never moves. A fixed nominal threshold in an inflating economy is a tax increase on autopilot: nobody votes on it, and it compounds annually. The same logic applies to the $250,000 joint threshold, which two resident incomes clear easily once both partners reach attending pay.
Key insight
When you model your long-run marginal rate, treat the 0.9 percent as permanent above the thresholds and treat the thresholds as fixed. Under current law, a physician earning $300,000 today and $300,000 in ten years pays the surtax on more real income in year ten, because the threshold will not have moved while the composition of that $300,000 has.
Your employer withholds by a rule that ignores your filing status
Here is the trap at the center of this article. Your employer does not withhold the surtax based on what you will actually owe. The rule, per IRS Topic 560 and the employer instructions in Publication 15 (2026), is mechanical: an employer must withhold Additional Medicare Tax on wages it pays to an employee in excess of $200,000 in a calendar year, without regard to filing status, beginning in the pay period in which wages cross $200,000 and continuing through year end.
Notice what that rule cannot see: your spouse's income, your other jobs, and your filing status. The result is that withholding and liability agree only by coincidence. Four physician scenarios show the mismatch:
| Scenario | Employer withholding | Actual liability | Result at filing |
|---|---|---|---|
| Two attendings, MFJ, each earning $180,000 | $0 (neither crosses $200,000) | $990 | Balance due |
| Single hospitalist, $150,000 W-2 plus $120,000 second W-2 | $0 | $630 (0.9% of $70,000 over the $200,000 threshold) | Balance due |
| One-earner couple, MFJ, $230,000 wages | $270 (0.9% of $30,000 over $200,000) | $0 (under $250,000) | Credited back |
| MFS physician earning $150,000 | $0 | $225 (0.9% of $25,000 over $125,000) | Balance due |
Employer withholding keys off a single employer's $200,000 wage line, while your actual liability keys off household income against the filing-status threshold — the two rules cannot agree, so the gap is structural, not an error. Form 8959, attached to your return, is where the truth comes out: it computes your actual Additional Medicare Tax, compares it with what was withheld, and either adds the shortfall to your bill or credits the excess against your total tax. The Form 8959 instructions confirm that over-withheld amounts are claimable as a credit, so the one-earner couple in row three is made whole — after lending the Treasury $270 interest-free for a year.
Example calculation
Assumptions, stated explicitly: married filing jointly; each spouse is a W-2 attending earning exactly $180,000 of Medicare wages in 2026; no self-employment income; no W-4 Step 4(c) additions.
Combined Medicare wages: $180,000 + $180,000 = $360,000 MFJ threshold: $250,000 Wages subject to the surtax: $360,000 − $250,000 = $110,000 Additional Medicare Tax owed: $110,000 × 0.9% = $990 Withheld by either employer: $0, because neither spouse individually crossed $200,000 Reconciled on Form 8959 at filing: $990 balance due
Important
In isolation, this couple's $990 shortfall slips under the section 6654 rule that waives the underpayment penalty when you owe less than $1,000 after withholding. Stack a moonlighting 1099, an under-withheld RVU bonus, or net investment income on top, and the combined shortfall clears $1,000 easily — at which point penalty exposure depends on the safe harbors covered in the withholding guide.
The mirror-image failure is just as common: a physician who changes employers mid-year and earns $150,000 at each has $300,000 of wages, owes the surtax as a single filer on $100,000, and has had nothing withheld, because each employer's counter reset to zero. If a raise or job change is what moved you across the line, the annualization mechanics in the mid-year raise article explain what the rest of your withholding is doing at the same time.
Moonlighting income does not get its own threshold
The surtax reaches self-employment income too, and the coordination rule is easy to get wrong in your favor. Under section 1401(b)(2), the threshold that applies to your self-employment income is reduced — but not below zero — by your Medicare wages. The Form 8959 instructions state the rule directly: the threshold for the self-employment calculation is reduced by the total amount of Medicare wages received.
Concretely: a single emergency physician with $150,000 of W-2 wages and $60,000 of net earnings from self-employment does not compare the $60,000 against a fresh $200,000 threshold. The W-2 wages consume $150,000 of it, leaving $50,000; the surtax applies to $60,000 − $50,000 = $10,000, or $90. Move the same physician to $190,000 of W-2 wages and the reduced threshold is $10,000, putting $50,000 of the moonlighting income in scope — $450, with nothing withheld anywhere. The moonlighting-income module covers the estimated-tax workflow this creates.
One asymmetry to file away: when you compute the deduction for one-half of self-employment tax, the 0.9 percent is excluded. The IRS self-employment tax page frames the deduction as the employer-equivalent portion of SE tax, and the Additional Medicare Tax has no employer equivalent — it is entirely yours, above and below the line.
The 3.8 percent sibling taxes your portfolio at the same frozen lines
The same 2013 legislation created the Net Investment Income Tax under section 1411: 3.8 percent on the lesser of your net investment income or the amount by which exceeds — the identical numbers — $250,000 MFJ, $125,000 MFS, $200,000 single or head of household (IRS Net Investment Income Tax page). A two-attending couple that owes the $990 above almost certainly also owes NIIT on every dollar of dividends, capital gains, and interest in their taxable account, because their MAGI clears $250,000 before the first investment dollar is counted. The two surtaxes are cousins, not the same tax: the 0.9 percent rides on earned income through payroll and Form 8959, while the 3.8 percent rides on investment income through Form 8960. Neither threshold will ever index under current law.
Two levers close the gap before April does
You cannot ask payroll to start the 0.9 percent early — the IRS Additional Medicare Tax Q&A is explicit that an employee may not request Additional Medicare Tax withholding on wages below $200,000. What the Q&A does endorse is the general-purpose fix: request additional income tax withholding on Form W-4, which is applied against your total liability, surtax included.
The arithmetic takes five minutes in December or June. Project combined household Medicare wages, subtract your filing-status threshold, multiply by 0.9 percent, subtract anything your employers will withhold on wages over $200,000, and divide the remainder by your remaining pay periods. That number goes on W-4 Step 4(c) as a flat dollar add-on per check. For the $360,000 couple above, $990 across the year is about $41 per semi-monthly check for one spouse — set once, correct forever, no estimated-payment vouchers. If a supplemental payment such as a signing or RVU bonus is what pushes you over, the flat-rate withholding rules in the supplemental wages article interact with this same gap.
Quick takeaway
The Additional Medicare Tax is not avoidable, but it is entirely predictable. The withholding system will not predict it for you, because employers withhold at a $200,000 per-employer trigger that knows nothing about your marriage, your second job, or your 1099s. Ten minutes with a pay stub and W-4 Step 4(c) converts an April surprise into a rounding error.
Common questions
Why is my employer withholding extra Medicare tax when my spouse does not work and we will not owe it?
Because the withholding rule is filing-status-blind. Once your wages from that employer cross $200,000, withholding at 0.9 percent is mandatory even if your joint liability will be zero because you are under the $250,000 MFJ threshold. You recover the excess at filing: Form 8959 computes actual liability, and over-withheld surtax becomes a credit against your total tax.
Do bonuses and call pay count toward the $200,000 trigger?
Yes. The trigger and the tax both apply to Medicare wages, which include supplemental payments such as signing bonuses, call stipends, and RVU reconciliation payouts. A $40,000 bonus in November can be exactly what pushes your year-to-date wages across $200,000 and switches the withholding on for the rest of the year.
Can I just have my moonlighting agency withhold the surtax?
If the moonlighting is work, there is no withholding agent at all — you cover the surtax through quarterly estimated payments or by raising W-4 withholding at your W-2 job. Remember that your W-2 wages reduce the threshold that applies to the self-employment income, so the surtax often applies to the first moonlighting dollar even when the moonlighting income itself is modest.
Is the 0.9 percent ever deductible?
No. The deduction for one-half of self-employment tax covers only the employer-equivalent portion of the 12.4 percent Social Security and 2.9 percent Medicare components. The 0.9 percent has no employer half, so no portion of it is deductible, whether you pay it through payroll or through self-employment tax.
What to do next
- Pull your most recent pay stub and, if married, your spouse's, and project total household Medicare wages for the year — the year-to-date Medicare wages line divided by pay periods elapsed, times total periods, is close enough.
- Compare the projection against your filing-status threshold: $250,000 MFJ, $200,000 single or head of household, $125,000 MFS.
- Compute the expected surtax — 0.9 percent of the excess — and subtract whatever will be withheld automatically at any single employer paying you over $200,000.
- Divide any shortfall by remaining pay periods and file a new W-4 with that amount on Step 4(c), or fold it into quarterly estimates if you already pay them for 1099 income.
- If you moonlight, reduce your threshold by projected W-2 Medicare wages before testing the self-employment income, and revisit the math whenever either income changes.
- At filing, confirm Form 8959 is attached any time your wages exceeded $200,000 or any surtax was withheld — that is where shortfalls are settled and excess withholding comes back.
The surtax rewards exactly one behavior: projecting household wages once a year and adjusting a single W-4 line. That protocol works with or without us. This is education, not individualized financial advice.