When Does the Additional Medicare Tax Kick In?

The Additional Medicare Tax kicks in once your wages or self-employment income for the year pass $200,000 if you file as single or head of household, $250,000 if you’re married filing jointly, or $125,000 if you’re married filing separately. It’s a flat 0.9% surtax that applies only to the dollars above your threshold, layered on top of the regular 1.45% Medicare tax. The thresholds are written into the tax code with no inflation adjustment, so more workers cross them each year.¹

The Thresholds by Filing Status

Your filing status sets the point at which the 0.9% starts applying:

Married filing jointly: $250,000
Married filing separately: $125,000
Single: $200,000
Head of household: $200,000
Qualifying surviving spouse: $200,000

Above the line, your combined Medicare tax rate is 2.35%. Below the line, nothing changes.²

A quick example. If you’re single with $230,000 in wages, the surtax applies to the $30,000 above your $200,000 threshold. That’s $270 in Additional Medicare Tax ($30,000 × 0.009).

What Income Counts Toward the Threshold

The tax applies to wages, salary, tips, and other compensation subject to FICA withholding, along with net self-employment earnings. If you have both, they’re combined when measured against your threshold. Non-cash fringe benefits and deferred compensation that appear in your FICA wages count too. Railroad Retirement Tax Act compensation follows the same rules and thresholds.³

Investment income is outside the scope entirely. Dividends, interest, capital gains, rental income, and royalties don’t count toward the Additional Medicare Tax threshold. Those categories fall under a separate surtax (the Net Investment Income Tax), and the two never overlap.

When Your Employer Starts Withholding

Your employer begins withholding the extra 0.9% the moment your year-to-date wages from that job hit $200,000. This is a mechanical rule. The employer ignores your filing status, your spouse’s income, and anything you earn elsewhere. It watches only the running total of what it has paid you.³

That $200,000 employer trigger stays the same whether your actual filing threshold is $125,000, $200,000, or $250,000. Which produces a predictable mismatch between what gets withheld and what you owe.

When Too Much Is Withheld

Married filing jointly, earning $210,000 from a single job? Your employer withholds the surtax on the $10,000 above $200,000, but your joint threshold is $250,000, so you don’t owe it. The $90 becomes a credit when you file.¹

When Too Little Is Withheld

This is where the surprise hits. Two jobs paying $150,000 each? Neither employer reaches the $200,000 trigger, so neither withholds anything extra. But your combined $300,000 exceeds the single threshold by $100,000, leaving a $900 tax bill nobody collected. Married couples filing separately hit the same problem when two modest incomes combine past $125,000.

The fix is Form W-4, line 4(c). Request a flat additional dollar amount withheld from each paycheck. It goes toward income tax withholding rather than Medicare withholding specifically, but the extra cash covers the gap so April doesn’t sting.

Bonuses and Mid-Year Crossings

The $200,000 employer trigger is cumulative for the calendar year. If a bonus pushes your year-to-date wages past $200,000, withholding begins with that paycheck, including on the portion of the bonus above the line. No special rate applies to supplemental wages; the surtax simply activates once cumulative compensation from that employer clears $200,000.³

Self-Employment Income

With no employer tracking a running total, self-employed taxpayers handle the full calculation themselves. The surtax applies to net self-employment earnings (profit after deductions, as figured on Schedule SE).

When you have wages and self-employment income together, the threshold gets reduced by your wages first, then applied to your self-employment income. The ordering matters. Single, with $180,000 in W-2 wages and $50,000 in net self-employment earnings: your $200,000 threshold shrinks by the $180,000 in wages, leaving $20,000. The surtax hits $30,000 of your self-employment income ($50,000 minus the $20,000 remaining), producing a $270 bill.

If your wages alone already exceed the threshold, every dollar of net self-employment income gets hit from the start.

Quarterly Estimated Payments

No one withholds this tax from self-employment income, so you cover it through quarterly estimated payments. For the 2026 tax year, the due dates are:

1st payment: April 15, 2026
2nd payment: June 15, 2026
3rd payment: September 15, 2026
4th payment: January 15, 2027

You can skip the January 15, 2027 installment if you file your 2026 return and pay the full balance by February 1, 2027.⁴

If your income fluctuates, the annualized income installment method on Schedule AI of Form 2210 lets you base each quarter’s payment on income actually earned during that period rather than guessing at the full year upfront.

Reconciling at Tax Time on Form 8959

Everything reconciles on Form 8959. You must file it if Medicare wages on any single W-2 exceed $200,000, or if your combined wages and self-employment income exceed the threshold for your filing status.⁵

The form runs your wages and self-employment income against your filing status threshold, calculates the 0.9% owed, and then compares that to what was already withheld. The total tax flows to Schedule 2 of Form 1040 (Line 11). The withholding credit goes to the payments section. The difference determines whether you owe more or get some back.

One quirk in the withholding calculation: your W-2 Box 6 combines the regular Medicare tax and the Additional Medicare Tax into a single figure. Form 8959 isolates the surtax portion by subtracting 1.45% of your Medicare wages (Box 5) from the total in Box 6.⁶

Avoiding an Underpayment Penalty

If you owe Additional Medicare Tax that wasn’t covered by withholding or estimated payments, the IRS can charge an underpayment penalty plus interest. The interest rate for underpayments was 7% per year (compounded daily) for the first quarter of 2026 and 6% for the second quarter; the rate resets quarterly.⁷

You avoid the penalty if you meet any of these safe harbors:

Your total tax minus withholding is less than $1,000.
You paid at least 90% of your current year’s total tax through withholding and estimated payments.
You paid at least 100% of your prior year’s total tax (110% if your prior-year adjusted gross income exceeded $150,000, or $75,000 if married filing separately).

The 110% prior-year safe harbor is usually the practical one for taxpayers newly crossing into Additional Medicare Tax territory. Paying 110% of last year’s total tax protects you from a penalty even if this year’s bill turns out much larger.⁸

The IRS can waive penalties in certain situations, including underpayments caused by a casualty or disaster, or if you retired after reaching age 62 or became disabled during the tax year.⁹

1
Internal Revenue Service. Questions and Answers for the Additional Medicare Tax
2
Office of the Law Revision Counsel. 26 U.S. Code 3101 – Rate of Tax
3
eCFR. 26 CFR 31.3102-4 – Special Rules Regarding Additional Medicare Tax
4
Internal Revenue Service. 2026 Form 1040-ES – Estimated Tax for Individuals
5
Internal Revenue Service. Instructions for Form 8959, Additional Medicare Tax
6
Internal Revenue Service. 2026 General Instructions for Forms W-2 and W-3
7
Internal Revenue Service. Quarterly Interest Rates
8
Internal Revenue Service. Underpayment of Estimated Tax by Individuals Penalty
9
Internal Revenue Service. Instructions for Form 2210