Additional Medicare Tax requires two separate calculations: what your employer must withhold from your paycheck and what you actually owe on your federal return. For tax years 2025 and 2026, the additional rate is 0.9%, but the employer’s withholding trigger is not necessarily your filing-status threshold. To check a paycheck, start with Medicare wages already paid by that employer during the same calendar year. To estimate annual liability, gather Medicare wages from all jobs and, for a joint return, your spouse’s amounts. IRS Topic 560 explains the distinction; the amounts for these two tax years appear in the 2025 Form 8959 instructions and 2026 Publication 505.
What are the Additional Medicare Tax thresholds?
For tax years 2025 and 2026, apply the following annual thresholds to Medicare wages and applicable self-employment income:
| Filing status | 2025 threshold | 2026 threshold |
|---|---|---|
| Single | $200,000 | $200,000 |
| Married filing jointly | $250,000 | $250,000 |
| Married filing separately | $125,000 | $125,000 |
| Head of household | $200,000 | $200,000 |
| Qualifying surviving spouse | $200,000 | $200,000 |
The additional rate is 0.9% for both tax years. These thresholds are not indexed for inflation. For married filing jointly, combine both spouses’ applicable amounts before comparing them with the joint threshold; each spouse does not receive a separate joint threshold. See the 2025 instructions and 2026 Publication 505.
The threshold applies to the relevant Medicare tax base—not taxable income after deductions, adjusted gross income (AGI), or modified adjusted gross income (MAGI). It is an excess-income threshold, not a phase-out: crossing it does not make all your wages subject to the additional tax. Form 8959 calculates the tax separately from the regular federal income tax tables.
Why can employer withholding differ from your final tax?
For 2025 and 2026, an employer must begin withholding Additional Medicare Tax when Medicare wages it pays an employee exceed $200,000 during the calendar year. Withholding starts in the paycheck that crosses that amount and applies only to the excess. The employer uses this trigger regardless of filing status, a spouse’s earnings, or wages from another employer. There is no employer match for the additional tax. IRS Topic 560 describes these payroll requirements.
The central distinction is withholding versus liability:
| Question | Employer payroll calculation | Federal return calculation |
|---|---|---|
| Whose wages count? | Generally, wages that employer pays that employee | Medicare wages from all employers; both spouses’ amounts on a joint return |
| Which threshold applies? | $200,000 for 2025 and 2026, regardless of filing status | The applicable annual filing-status threshold above |
| Does self-employment income affect it? | Not the employer’s withholding trigger | Yes; wages reduce the threshold remaining for self-employment income |
| What does the result represent? | Tax withheld through payroll | Additional Medicare Tax liability reconciled with withholding on Form 8959 |
These distinctions follow the Form 8959 instructions. An employer can correctly withhold nothing even though you owe the tax, or correctly withhold an amount even though your final Additional Medicare Tax liability is zero.
Which prior year-to-date wages do you need?
For a paycheck calculation, “prior year-to-date wages” means Medicare wages paid earlier in the current calendar year, before the paycheck being tested. It does not mean wages from the previous tax year.
Gather these inputs:
- Medicare wages already paid by the employer before the current paycheck.
- Medicare-taxable wages and tips included in the current paycheck.
- The calendar year to which those payments belong.
Use the Medicare wage figure from payroll records—not take-home pay or a wage figure used only for federal income tax withholding. At year-end, Form W-2 box 5 reports Medicare wages and tips. The Form 8959 instructions use box 5 rather than box 1 for this calculation.
Under the ordinary separate-employer rule, do not add an unrelated former employer’s wages to a new employer’s payroll withholding trigger. Those wages still count when calculating your annual liability. If a business acquisition or payroll arrangement carries forward earlier wages, confirm the employer’s treatment rather than assuming the ordinary separate-employer formula applies.
For 2025 or 2026, the basic paycheck formula is:
[
H=0.009\times
\left[
\max(Y+P-200{,}000,0)-\max(Y-200{,}000,0)
\right]
]
Here, (H) is Additional Medicare Tax withholding for the current paycheck in dollars, (Y) is that employer’s Medicare wages paid before the paycheck, and (P) is the current paycheck’s Medicare wages. The formula applies the IRS requirement to withhold only on wages above the annual employer trigger.
Hypothetical example: a paycheck crosses the trigger
Assume an employee has $198,000 of Medicare wages from one employer before a $6,000 Medicare-taxable paycheck in 2025. Assume no payroll corrections or special wage-carryover arrangement.
- Medicare wages after the paycheck: $198,000 + $6,000 = $204,000.
- Wages above the 2025 employer trigger: $204,000 − $200,000 = $4,000.
- Additional Medicare Tax withheld: $4,000 × 0.009 = $36.00.
Only $4,000 of this paycheck is subject to additional withholding. The result does not establish the employee’s annual liability because filing status, other jobs, and a spouse’s income may change the return calculation. This example applies the IRS employer withholding rule.
How do you calculate annual Additional Medicare Tax?
For an employee with Medicare wages only, use:
[
A=r\times\max(W-T,0)
]
Where:
- (A) is annual Additional Medicare Tax in dollars.
- (W) is total annual Medicare wages and tips included in the calculation.
- (T) is the filing-status threshold for that tax year.
- (r) is 0.009 for tax years 2025 and 2026.
For a joint return, (W) includes both spouses’ applicable wages. Do not subtract Additional Medicare Tax withholding before applying the formula; withholding is reconciled afterward.
For the 2025 return, Form 8959 builds the wage total from all W-2 box 5 amounts, plus applicable unreported tips from Form 4137 line 6 and wages from Form 8919 line 6. Use the final instructions for the actual year being filed before relying on line references for another year.
Hypothetical example: two jobs, no additional withholding
Assume a single employee has these 2025 amounts:
| Input | Amount |
|---|---|
| Medicare wages from Employer A | $140,000 |
| Medicare wages from unrelated Employer B | $90,000 |
| Self-employment income | $0 |
| RRTA compensation | $0 |
| Additional Medicare Tax withheld | $0 |
Neither employer pays the employee more than the 2025 employer trigger, so neither withholds Additional Medicare Tax. The annual calculation is different:
- Combine Medicare wages: $140,000 + $90,000 = $230,000.
- Subtract the 2025 single threshold: $230,000 − $200,000 = $30,000.
- Multiply the excess by the 2025 additional rate: $30,000 × 0.009 = $270.
- Subtract Additional Medicare Tax withholding: $270 − $0 = $270.
The employee has $270 of Additional Medicare Tax liability not covered by Additional Medicare withholding. That is not necessarily the amount due with the full federal return: other withholding, estimated payments, credits, and taxes also affect that result.
The reverse can happen, too. In a hypothetical 2025 joint return, one spouse earns $230,000 from one employer and the other has no wages or self-employment income. The employer withholds $270 on wages above its $200,000 trigger, but the couple’s wages remain below the 2025 joint threshold of $250,000. Their Additional Medicare Tax liability is zero, and Form 8959 reconciles the $270 as withholding available against total federal tax—not as a guaranteed standalone refund.
What changes if you also have self-employment income?
Do not substitute gross freelance receipts for the self-employment input. For 2025, the Form 8959 instructions direct taxpayers to Schedule SE, Part I, line 6, and exclude negative amounts from this calculation. A self-employment loss does not offset Medicare wages for Additional Medicare Tax purposes.
When wages and positive self-employment income are both present, calculate:
[
R=\max(T-W,0)
]
[
A_{\mathrm{SE}}=r\times\max(S-R,0)
]
Here, (R) is the threshold remaining after Medicare wages, (S) is the applicable positive self-employment income, and (A_{\mathrm{SE}}) is the additional tax on that income. Add this result to the additional tax on wages. For 2025 and 2026, (r=0.009).
Railroad Retirement Tax Act (RRTA) compensation follows a separate comparison with the filing-status threshold. Do not simply combine RRTA compensation with Medicare wages and self-employment income into one total.
What should you enter in the calculator—and check separately?
The Additional Medicare Tax Calculator uses annual Form 8959-style inputs, not a single paycheck and prior year-to-date payroll inputs. Enter annual Medicare wages, applicable self-employment income, any RRTA compensation, filing status, and withholding records. During the year, use projected full-year amounts rather than entering year-to-date wages alone as if they were the final annual total. The tool estimates this federal tax component; it does not calculate employer payroll withholding or the full federal return.
Check the withholding estimate separately when your records include more than ordinary W-2 wages:
- The calculator subtracts regular Medicare tax of 1.45% from its entire Form 8959 wage input when estimating the additional portion of W-2 box 6 withholding.
- The 2025 IRS form instead calculates that regular withholding amount using W-2 box 5 wages from Form 8959 line 1—not the broader line 4 total that can include Forms 4137 and 8919.
- The 2025 instructions also require certain W-2 box 12 code B and code N amounts in the withholding reconciliation, while the calculator’s input is labeled as a box 6 total.
Consequently, the calculator’s withholding credit may differ from Form 8959 when these additional items are present. Use the official form and to reconcile those records rather than treating the estimate as a completed return.
Keep cents in planning calculations. If rounding to whole dollars on a 2025 return, follow the Form 1040 instructions: use whole-dollar rounding consistently, drop amounts below 50 cents, and increase amounts from 50 through 99 cents to the next dollar. When combining amounts for one line, add them before rounding.
How can you address a projected withholding shortfall?
If the annual estimate exceeds expected Additional Medicare Tax withholding, review total federal payments—not just this tax component. The IRS permits employees to request additional federal income tax withholding through Form W-4 or, when appropriate, make estimated tax payments. You cannot request extra withholding specifically designated as Additional Medicare Tax, and you cannot ask an employer to stop additional withholding that the law requires.
For 2026 planning, Publication 505 explains how to evaluate withholding and estimated payments together. Whether an underpayment penalty applies depends on the broader payment calculation and timing, not merely on whether Additional Medicare Tax remains unpaid. Use the publication for the relevant payment year and the final Form 8959 instructions for the return year; the calculator does not submit a W-4, make payments, or prepare or file the return.