Additional Medicare + NIIT Stacking Calculator
Combine the 0.9% Additional Medicare Tax + 3.8% NIIT in one calculator. Both surcharges apply to high earners and frequently stack.
Two Stacking Surcharges Most High Earners Don't Plan For
Both surcharges entered the tax code via the Affordable Care Act (2010) and took effect January 1, 2013. The 0.9% Additional Medicare Tax (Section 3101(b)(2)) applies to wages, SE income, and railroad compensation. The 3.8% NIIT (Section 1411) applies to investment income. Critically, both share the SAME income thresholds: $200K single, $250K MFJ, $200K HoH, $125K MFS. And both thresholds are NOT indexed to inflation — they capture more households each year as wages grow.
Most high earners pay BOTH simultaneously. A single filer with $280K wages and $40K investment income owes: $720 Additional Medicare (0.9% on the $80K over $200K wages) PLUS $4,560 NIIT (3.8% on the lesser of $40K investment income or $120K AGI overage = $40K). Combined surcharge: $5,280. Source: IRS Section 1411, Section 3101(b)(2). Last updated: May 2026.
How to Avoid Stacking (or Minimize It)
(1) Maximize tax-advantaged accounts. 401(k) + HSA + IRA reduce both wages (lower Add'l Medicare) AND AGI (lower NIIT exposure). (2) Tax-loss harvesting. Reduces investment income subject to NIIT. (3) Muni bonds. Tax-exempt interest is NOT investment income for NIIT. (4) Roth conversions in low-AGI years. Permanently moves money out of NIIT-subject investment income. (5) Real estate professional status. Rental income reclassified as active = exempt from NIIT.
Stacking With Other High-Earner Taxes
For ultra-high earners, the surcharges compound with: (1) Top 37% federal income tax bracket. (2) AMT (often deactivated by TCJA but can apply). (3) State income tax 5-13%. (4) Phase-out of itemized deductions. Combined marginal rate on the next dollar earned by a high earner in CA or NY easily reaches 50%+.
Form 8959 + Form 8960 Filing
Additional Medicare Tax: file Form 8959 with your 1040. NIIT: file Form 8960. Both flow to your Form 1040 line 23 'Other Taxes' via Schedule 2. Most tax software auto-calculates these — verify the numbers, especially if you have multi-state income or unusual investment situations.
Frequently Asked Questions
When did Additional Medicare Tax and NIIT take effect?
Both went into effect January 1, 2013, via the Affordable Care Act (Section 1411 NIIT, Section 3101(b)(2) Additional Medicare Tax). Together they primarily fund Medicare and ACA expansion costs.
Are the thresholds adjusted for inflation?
No \u2014 both surcharges have FIXED thresholds unchanged since 2013. As wages rise, more households cross into surcharge territory each year. Congress could index them but has not done so.
Can I owe Additional Medicare Tax without owing NIIT (or vice versa)?
Yes \u2014 they're separate. Additional Medicare applies to earned income; NIIT applies to investment income. A high-wage earner with no investments owes only Add'l Medicare. A retiree with no wages but investment income owes only NIIT. Most working high earners owe both.
Do retirement account withdrawals trigger these taxes?
401k/IRA withdrawals are NOT subject to NIIT or Additional Medicare Tax. This is one of the strongest tax advantages of retirement accounts \u2014 every dollar inside escapes both surcharges forever.
What about my state \u2014 do they have similar surcharges?
Some states have similar high-earner surcharges. California has a 13.3% top rate (highest in US). New York has a 9.65-10.9% surcharge above $1M. New Jersey has a 'millionaire's tax' at 10.75%. Total effective rate at top brackets in CA/NY can reach 50%+ combined federal + state.
Can I avoid both surcharges by moving to no-income-tax state?
You can avoid STATE surcharges but not federal. Federal Add'l Medicare + NIIT apply regardless of state residence. Texas, Florida, Tennessee, Washington, Nevada, South Dakota, Wyoming, Alaska, New Hampshire have no state income tax \u2014 saves 5-13% on the next dollar.