Net Investment Income Tax (2026)
Estimate the 3.8% Net Investment Income Tax on the lesser of net investment income or MAGI over statutory thresholds.
Calculator
NIIT applies to the lesser of NII or MAGI over $200k/$250k thresholds.
Net Investment Income Tax
High-income taxpayers may owe an additional 3.8% tax on net investment income (NII) or on MAGI over statutory thresholds—whichever bite is smaller. Thresholds are approximately $200,000 single/head of household, $250,000 married filing jointly, and $125,000 married filing separately.
NII includes interest, dividends, capital gains, rental income (non-business), and passive activity income, minus allowable deductions. Wages and self-employment earnings are not NII but can push MAGI over the threshold, triggering NIIT on investment income.
How to use the calculator
Enter MAGI, net investment income, and filing status. Tax base = min(NII, MAGI − threshold). NIIT = 3.8% × base.
Stacking with other taxes
Capital gains already face 0%/15%/20% rates—NIIT stacks on top for affected dollars. Roth conversions increase MAGI without adding NII but can trigger NIIT on existing NII by crossing thresholds.
Related tools
Capital gains tax calculator, dividend tax calculator, Roth conversion calculator, IRMAA calculator.
2026 context
The 2026 standard deduction is $16,100 for single and married filing separately filers, $24,150 for head of household, and $32,200 for married filing jointly (IRS Rev. Proc. 2025-32).
Sources
IRC §1411; Form 8960. Rev. Proc. 2025-32 bracket context for ordinary stacking.
Documentation and recordkeeping
Keep copies of forms, notices, and account statements that support numbers you enter. IRS audits and state reviews often start with mismatches between third-party reporting and what you claimed. Reconcile calculator outputs to official worksheets before filing.
When to revisit your estimate
Life changes mid-year—marriage, divorce, a move, bonus income, or a new job—can shift brackets, credits, and phaseouts. Rerun the tool when those events occur rather than relying on a January estimate through December.
State and local taxes
This page focuses on federal rules unless noted. Many states piggyback on federal AGI or MAGI definitions but apply their own rates and credits. Pair federal estimates with the state income tax calculator when residency matters.
Professional guidance
Complex returns—AMT, NIIT, multi-state income, business ownership, or large conversions—benefit from a CPA or enrolled agent who can sign the return. Calculators here show the math chain; they do not replace personalized advice or e-file validation.
Methodology on this site
Core 2026 federal brackets, deductions, and payroll limits follow IRS Rev. Proc. 2025-32, SSA wage-base announcements, and CMS Medicare premium tables where applicable. We show assumptions in the result panel when a rule is simplified for education.
Quarterly check-ins
Retirees and self-employed filers should revisit estimates after each quarter when investment income, required distributions, or business profit shifts. Waiting until December limits your options for withholding adjustments and timely estimated payments.
Documentation and recordkeeping
Keep copies of forms, notices, and account statements that support numbers you enter. IRS audits and state reviews often start with mismatches between third-party reporting and what you claimed. Reconcile calculator outputs to official worksheets before filing.
When to revisit your estimate
Life changes mid-year—marriage, divorce, a move, bonus income, or a new job—can shift brackets, credits, and phaseouts. Rerun the tool when those events occur rather than relying on a January estimate through December.
State and local taxes
This page focuses on federal rules unless noted. Many states piggyback on federal AGI or MAGI definitions but apply their own rates and credits. Pair federal estimates with the state income tax calculator when residency matters.
Professional guidance
Complex returns—AMT, NIIT, multi-state income, business ownership, or large conversions—benefit from a CPA or enrolled agent who can sign the return. Calculators here show the math chain; they do not replace personalized advice or e-file validation.
Methodology on this site
Core 2026 federal brackets, deductions, and payroll limits follow IRS Rev. Proc. 2025-32, SSA wage-base announcements, and CMS Medicare premium tables where applicable. We show assumptions in the result panel when a rule is simplified for education.
Quarterly check-ins
Retirees and self-employed filers should revisit estimates after each quarter when investment income, required distributions, or business profit shifts. Waiting until December limits your options for withholding adjustments and timely estimated payments.
Reading official publications
IRS Publications and Instructions often walk through worksheets line by line. When our simplified path differs from a form worksheet, trust the form for filing and use this page for directional planning only.
Calculator directory
Browse related tools from the calculator directory when your question spans credits, payroll, retirement, and investment tax in the same year.
Withholding versus liability
Paycheck withholding and estimated tax payments are cash-flow tools. They are not the same as annual tax liability computed on the return. Use the W-4 withholding calculator and quarterly estimated tax calculator when you need payment timing, not just liability.
Standard deduction reminder
The 2026 standard deduction is $16,100 for single and married filing separately filers, $24,150 for head of household, and $32,200 for married filing jointly (IRS Rev. Proc. 2025-32). Itemized filers must beat those amounts on Schedule A for itemizing to win.
Documentation and recordkeeping
Keep copies of forms, notices, and account statements that support numbers you enter. IRS audits and state reviews often start with mismatches between third-party reporting and what you claimed. Reconcile calculator outputs to official worksheets before filing.
When to revisit your estimate
Life changes mid-year—marriage, divorce, a move, bonus income, or a new job—can shift brackets, credits, and phaseouts. Rerun the tool when those events occur rather than relying on a January estimate through December.
State and local taxes
This page focuses on federal rules unless noted. Many states piggyback on federal AGI or MAGI definitions but apply their own rates and credits. Pair federal estimates with the state income tax calculator when residency matters.
Frequently asked questions
Is this niit calculator free?
Yes. US Tax Tools calculators run free in your browser with no account required. Results are educational estimates with visible assumptions.
Do these amounts match IRS publications?
Core TY2026 federal figures follow Rev. Proc. 2025-32 and companion IRS/SSA announcements as of the site verification date. User-supplied rates (for example HTS duty %) are never invented—enter them from primary sources.
When should I talk to a tax pro?
Before large Roth conversions, entity changes, or cross-border moves—and anytime a calculator warning flags simplified data or user-supplied rates.
Do you fill missing fields with averages?
No. Prefer an explicit user entry over a silent national average that hides your facts.
Can I model state tax too?
This page emphasizes federal rules. Pair with the state income tax calculator when state residency affects your plan.
Government sources
- IRS — Revenue Procedure 2025-32 — Tax Year 2026 Inflation Adjustments (including OBBBA amendments) Accessed 2026-07-20 · Effective 2026-01-01
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Tax year 2026 · Last reviewed 2026-07-20 · Reviewed by US Tax Tools editorial · Methodology