At a glance
Quick answer
Additional Medicare Tax is a 0.9% employee tax on Medicare wages, self employment income, and railroad retirement compensation above the applicable filing status threshold. This calculator models Form W-2 box 5 wages and tips, Form 4137 line 6 unreported tips, Form 8919 line 6 wages, and Schedule SE, Part I, line 6 income. It compares that return liability with a wage derived estimate of employer withholding. Employers start withholding only after one payroll pays an employee more than $200,000 of Medicare wages in the calendar year. RRTA compensation follows a separate Form 8959 calculation and is not included in this result.
How the calculation works
Calculate the wage portion first
Add Form W-2 box 5 Medicare wages and tips, Form 4137 line 6 unreported tips, and Form 8919 line 6 wages. For married filing jointly, also add the spouse's amounts from those lines. Compare that Form 8959 wage total with the return threshold: $200,000 for single, head of household, or qualifying surviving spouse; $250,000 for married filing jointly; and $125,000 for married filing separately. Multiply only the positive wage excess by 0.9%. Spouse amounts are ignored for nonjoint filing statuses.
Reduce the threshold before self employment income
Form 8959 applies its wage total before self employment income. Subtract combined Form 8959 wages from the filing status threshold. The reduced threshold is not below zero. Compare combined Schedule SE, Part I, line 6 income with that reduced amount, then multiply the positive excess by 0.9%. Combine line 6 from multiple Schedules SE when applicable. A self employment loss is treated as zero. The input is Schedule SE line 6 income, not Schedule C net profit, gross receipts, or the deductible half of regular self employment tax.
Estimate withholding one payroll at a time
For each entered employer, compare that employer's Form W-2 box 5 Medicare wages for one employee with $200,000. Form 4137 line 6 and Form 8919 line 6 increase return liability but do not increase this wage derived employer withholding estimate. The employer does not adjust the trigger for filing status, another employer, a spouse, or self employment income. The calculator supports two employer records for each spouse on a joint return and assumes they are separate unrelated payrolls. Qualifying predecessor and successor employers, a common paymaster, or some third party payer arrangements can require combined wage treatment. This is a wage derived estimate. Actual Additional Medicare Tax withholding is determined on Form 8959, line 24, from payroll records including Form W-2 box 6.
Read the difference as planning information
Modeled return liability minus estimated employer withholding can be positive or negative. A positive amount suggests the modeled tax is greater than the wage derived withholding estimate. A negative amount means the estimate exceeds modeled liability. Neither result is a payroll error finding or a guaranteed refund. Publication 505 explains additional income tax withholding and estimated tax payments when a taxpayer expects a balance.
Keep other taxes and deductions separate
Regular 1.45% employee Medicare tax applies independently and is not included in this 0.9% result. Social Security, federal income tax, and the 3.8% Net Investment Income Tax use different bases and rules. An income tax deduction does not reduce Form 8959 wages or Schedule SE line 6 income. Additional Medicare Tax has no employer match. RRTA compensation is separately compared with the filing status threshold in Form 8959, Part III, and is not modeled here.
2025 and 2026 values
Tax year 2025
2025 final Additional Medicare values
The final 2025 Form 8959 rate is 0.9%. Return thresholds are $200,000 for single, head of household, or qualifying surviving spouse; $250,000 for married filing jointly; and $125,000 for married filing separately. Employer withholding begins only on one employee's Medicare wages above $200,000 from that payroll.
Tax year 2026
2026 planning Additional Medicare values
The 2026 planning selection retains the statutory 0.9% rate and filing status thresholds. IRS Publication 15 for 2026 also retains the separate $200,000 employer withholding trigger. The 2026 selection remains labeled as planning because the final return form and filing instructions are not yet the selected year's final filing record.
Recalculate it yourself
Worked example
Wages reduce the threshold before self employment income
A single filer has $150,000 of Medicare wages from one employer and $60,000 from Schedule SE, Part I, line 6, in 2025.
- Wage liability = max($150,000 minus $200,000, $0) multiplied by 0.9% = $0.
- Reduced self employment threshold = $200,000 minus $150,000 wages = $50,000.
- Taxable self employment income = $60,000 minus $50,000 = $10,000.
- Self employment liability = $10,000 multiplied by 0.9% = $90.
- Estimated employer withholding = max($150,000 minus $200,000, $0) multiplied by 0.9% = $0.
Result
The modeled Form 8959 liability is $90, all from self employment income after wages reduce the available threshold. Wage derived employer withholding is $0, so the modeled difference is $90.
What is included
- Form W-2 box 5 Medicare wages and tips from up to two employers for the taxpayer and, on a joint return, up to two employers for the spouse; taxpayer and joint spouse totals from Form 4137 line 6 and Form 8919 line 6; combined Schedule SE line 6 income; filing status thresholds; separate wage and self employment liability at 0.9%; wage derived employer withholding; and the modeled difference.
- Final 2025 and planning 2026 values, including the separate $200,000 employer withholding trigger. Active money inputs are limited to a combined $1 trillion so cents remain exact within the calculator contract.
What is not included
- Regular 1.45% Medicare, Social Security, Net Investment Income Tax, federal and state income tax, AMT, income tax deductions, employer matching, payroll corrections, and a complete estimated tax payment recommendation.
- RRTA compensation and withholding are not included. Form 8959, Part III, compares RRTA compensation separately with the filing status threshold rather than combining it with Medicare wages or self employment income. The route also does not decide whether entered amounts are legally subject to Medicare or self employment tax.
Common mistakes
Using $200,000 as every return threshold
The employer trigger is always $200,000, but joint return liability begins above $250,000 and married-separate liability above $125,000.
Entering Schedule C profit on the Form 8959 line
The self employment input is Schedule SE, Part I, line 6. It is not gross receipts or unadjusted net profit, and a loss does not reduce wages for this tax.
Treating modeled withholding as the return credit
The calculator derives an estimate from entered employer wages. Use actual payroll records and Form 8959, line 24, for the return credit.
Expecting an employer match
Additional Medicare Tax is employee-only. The employer withholds when required but does not pay a matching 0.9% share.
Frequently asked questions
What does the Additional Medicare Tax calculator compare?
It models Form 8959 liability on entered Form W-2 box 5 wages, Form 4137 line 6 unreported tips, Form 8919 line 6 wages, and Schedule SE line 6 income, then compares that liability with a wage derived estimate from employer W-2 wages.
Why can liability differ from employer withholding?
An employer begins withholding after its payroll pays one employee more than $200,000 of Medicare wages, regardless of filing status, another job, a spouse, self employment income, or liability only Form 4137 and Form 8919 amounts.
Is Additional Medicare Tax the same as regular Medicare tax?
No. Regular Medicare tax applies separately. Additional Medicare Tax is an extra employee tax above applicable thresholds and has no matching employer share.
How does self employment income affect Additional Medicare Tax?
Medicare wages use the filing status threshold first. The remaining threshold, but not less than zero, is then applied to combined Schedule SE line 6 income.
Does the Additional Medicare Tax calculator include RRTA compensation?
No. Form 8959 compares RRTA compensation separately with the filing status threshold. This route does not model RRTA liability or RRTA withholding.
Primary sources
- 2025 Form 8959, Additional Medicare Tax, opens in a new tab
Reviewed 2026-07-25
- 2025 Instructions for Form 8959, opens in a new tab
Reviewed 2026-07-25
- 2025 Instructions for Schedule SE, opens in a new tab
Reviewed 2026-07-24
- IRS Questions and answers for the Additional Medicare Tax, opens in a new tab
Reviewed 2026-07-25
- IRS Topic 560, Additional Medicare Tax, opens in a new tab
Reviewed 2026-07-25
- IRS Topic 751, Social Security and Medicare withholding rates, opens in a new tab
Reviewed 2026-07-25
- IRS Publication 15 (Circular E), Employer's Tax Guide for 2025, opens in a new tab
Reviewed 2026-07-25
- IRS Publication 15 (Circular E), Employer's Tax Guide for 2026, opens in a new tab
Reviewed 2026-07-25
- IRS Publication 505, Tax Withholding and Estimated Tax for 2025, opens in a new tab
Reviewed 2026-07-25