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    Net Investment Income Tax (NIIT) Calculator (2026)

    §1411 imposes a 3.8% surtax on the lesser of (a) your net investment income or (b) your MAGI excess over the threshold. Thresholds are fixed by statute and not inflation-indexed: $200k single, $250k MFJ, $125k MFS.

    Guidance, not advice. This calculator runs the rules as published, it doesn't assess your circumstances. Your actual tax may be affected by factors it doesn't cover (deductions, credits, filing status nuances, state-specific adjustments). Always seek financial or tax advice from a qualified CPA, Enrolled Agent, or tax attorney, or contact the IRS. Read our editorial scope →

    Not inflation-indexed
    The NIIT thresholds ($200k single / $250k MFJ / $125k MFS) are fixed by statute. They do not adjust for inflation. Each year, more taxpayers cross the threshold even without real income growth.

    Filing status & MAGI

    MAGI = AGI + excluded foreign income. Your MAGI determines the threshold.

    $

    Same as AGI for most filers; add excluded foreign income if applicable.

    Net Investment Income (NII) categories

    Enter each category of investment income. The sum is your total NII.

    $

    Savings, CDs, bonds

    $

    Qualified and ordinary

    $

    Net gains ( LT + ST )

    $

    Schedule E, not REP

    $

    Not materially participated

    $

    Distributions (excess of basis)

    $

    Intellectual property

    $

    Trust/estate income, etc.

    Total NII$73,000

    What is not NII

    These income types do not count toward NII.

    • W-2 wages and self-employment income (Schedule C)
    • S-Corp distributions (non-wage portion)
    • Partnership income where you materially participate
    • Social Security benefits
    • IRA / 401(k) distributions
    • Tax-exempt municipal bond interest
    • Excluded gain on sale of principal residence (§121)

    NIIT owed

    3.8% × lesser of NII or MAGI excess over threshold.

    $2,774

    Binding constraint: NII — the lesser of $73,000 (NII) and $80,000 (MAGI − threshold).

    NIIT calculation walkthrough

    Net Investment Income (NII)$73,000
    MAGI$280,000
    − Threshold (SINGLE)−$200,000
    = MAGI excess$80,000
    Lesser of (a) and (b)$73,000
    × NIIT rate× 3.8%
    NIIT$2,774
    Real estate professional (REP) exclusion
    If you qualify as a real estate professional and materially participate in your rental activity, that rental income is excluded from NII. You must meet the 750-hour test and the material participation tests under §469. This can significantly reduce or eliminate NIIT for real estate investors.