W-2 Box 6 — Medicare tax withheld
1.45% of Box 5, plus 0.9% Additional Medicare Tax on the portion of Box 5 above $200,000 at any single employer.
At a glance — Box 6
- Box name
- Medicare tax withheld
- Reports to
- Feeds Form 8959 (Additional Medicare Tax); not on 1040 directly.
- Check against
- Box 5 × 1.45%, plus 0.9% × (Box 5 − $200,000) if Box 5 from this employer exceeds $200,000. There is no wage-base cap on the 1.45% portion — Medicare tax applies to every dollar of Box 5.
What Box 6 means
Box 6 reports the Medicare tax actually withheld from your pay. On the first $200,000 of Box 5 wages from a given employer, the rate is a flat 1.45% under IRC §3101(b)(1) — no cap, no filing-status variation. Once Box 5 wages from that employer cross $200,000 in the year, IRC §3101(b)(2) requires an additional 0.9% withheld on the excess, so the marginal payroll rate above $200,000 is 2.35%. Your employer matches the 1.45%, but there is no employer match for the 0.9% — that surcharge is employee-only.
The $200,000 withholding trigger applies per employer and is completely mechanical — it doesn't know your filing status or what any other employer paid you. Your real Additional Medicare Tax liability is computed separately, on Form 8959, against your actual filing-status threshold: $200,000 for single or head of household, $250,000 for married filing jointly, $125,000 for married filing separately. Because the withholding trigger and the liability threshold aren't the same number for joint and separate filers, over- and under-withholding are both common.
A single employer paying you just over $200,000 will withhold the 0.9% even if your MFJ threshold is $250,000 and you don't actually owe it yet — Form 8959 catches that and turns it into a credit reconciled through your withholding, the same as excess federal income tax. The opposite case is a genuine underpayment: two employers who each pay you under $200,000, so neither withholds the surcharge, but your combined wages exceed your MFJ or MFS threshold — Form 8959 calculates the amount you now owe.
This reconciliation path is different from Box 4's. Excess Social Security tax from multiple employers is claimed as a credit on Form 1040, Schedule 3, Line 11. Excess Additional Medicare Tax withholding has no equivalent Schedule 3 line — it's resolved entirely within Form 8959, whose net result flows into Form 1040, Line 25c, combined with your regular federal income tax withholding rather than as a separate credit.
Tax return implications
- Box 6 (specifically the Medicare tax withheld figure) is entered on Form 8959, which reconciles Additional Medicare Tax against your actual filing-status threshold.
- The reconciled result from Form 8959 is combined with your federal income tax withholding on Form 1040, Line 25c — unlike Box 4's excess, it does not get its own Schedule 3 line.
- Over-withholding (one employer withheld the 0.9% on wages under your actual MFJ/MFS threshold) produces a credit through that same Form 8959 → Line 25c path.
- Under-withholding (multiple employers, each under $200,000, that together exceed your threshold) means Form 8959 calculates additional tax you owe with your return.
- Box 6 has no effect on Social Security benefits — Medicare tax funds Medicare Part A only, and unlike Box 4, none of it is ever recoverable through Schedule 3.
Common pitfalls & things to check
- Don't confuse Box 6 with Box 4's excess-tax mechanism — excess Social Security tax from multiple employers goes on Schedule 3, Line 11; excess Additional Medicare Tax withholding does not — it's reconciled only on Form 8959.
- Don't confuse Box 6 (payroll Medicare tax) with the 3.8% Net Investment Income Tax on Form 8960 — NIIT applies to investment income, not wages, and has nothing to do with this box.
- Box 6 can look disproportionately large next to Box 2 (federal income tax) because Medicare tax has no deductions, exemptions, or brackets — it's a flat percentage of gross Medicare wages.
- Multiple jobs each under $200,000 can still leave you owing Additional Medicare Tax at filing if your combined wages exceed your MFJ ($250,000) or MFS ($125,000) threshold — check Form 8959 rather than assuming Box 6 already covered it.
- The employer never matches the 0.9% portion — if you're reconciling employer FICA costs against your own withholding, don't expect symmetry above $200,000 the way there is on the 1.45% base rate.
FAQ
Is excess Medicare tax withholding refunded the same way as excess Social Security tax?
No. Excess Social Security tax from multiple employers is claimed on Schedule 3, Line 11. Excess Additional Medicare Tax withholding has no Schedule 3 equivalent — it's reconciled only on Form 8959, which feeds Form 1040, Line 25c.
Why did my employer withhold the 0.9% Additional Medicare Tax if I don't think I owe it?
Employers must withhold it on any employee's wages over $200,000 from that employer, regardless of filing status. Your actual liability is settled on Form 8959, which can turn over-withholding into a credit.
I have two jobs, each paying under $200,000 — could I still owe Additional Medicare Tax?
Yes, if your combined wages exceed your filing-status threshold ($250,000 MFJ, $125,000 MFS, $200,000 single/HoH). Neither employer withholds it individually, so Form 8959 calculates what you owe.
Does my employer match the 0.9% Additional Medicare Tax?
No. Employers match the 1.45% base Medicare rate, but the 0.9% Additional Medicare Tax is employee-only — there is no employer counterpart.
Related W-2 boxes
Box 5 — Medicare wages and tips
Your wages subject to Medicare tax. Unlike Social Security, there is no wage base cap — Box 5 can exceed Box 3 on high salaries.
Box 1 — Wages, tips, other compensation
Your taxable federal wages for the year — gross pay minus pre-tax deductions like traditional 401(k), Section 125 cafeteria plan contributions, and pre-tax HSA.
Box 2 — Federal income tax withheld
Total federal income tax your employer withheld from your paychecks during the year, based on your Form W-4 elections.
Box 3 — Social security wages
Your wages subject to Social Security tax, capped at the annual wage base. Differs from Box 1 because traditional 401(k) deferrals are not excluded.
Reconciling your W-2 at tax time? Use the paycheck calculator to verify expected federal, Social Security, and Medicare withholdings on your salary, and the federal income tax calculator to estimate your refund or balance owing before you file.
Related Calculators
Paycheck Calculator
Federal, state, FICA withholding, net take-home, W-4 alignment
Federal Income Tax Calculator
10–37% brackets, $15,750 standard deduction, progressive calculation
W-4 Withholding Calculator
Form W-4 steps, correct federal withholding, avoid penalties
FICA & Social Security
6.2% SS to $176,100, 1.45% Medicare, 0.9% additional Medicare
Tax Refund Estimator
Estimate federal refund, withholding vs liability, adjustments
401(k) Calculator
Contribution limits, employer match, tax-deferred growth
Sources
W-2 box definitions per IRS General Instructions for Forms W-2 and W-3 and IRC §6051. Rates and thresholds current for tax year 2025 (file by April 15, 2026); 2026 figures included where published.