Net Investment Income Tax Calculator
Net eligible investment streams, measure modified adjusted gross income above the statutory filing-status threshold, and apply 3.8% to the lesser amount.
Pour income through the NIIT sieve
Use annual federal amounts. The categories are planning inputs, not replacements for Form 8960 line classifications.
Estimated 3.8% Net Investment Income Tax
$48,000 is the lesser of net investment income and $60,000 of MAGI above the threshold.
Single / head-of-household threshold: $200,000.00
The two independent limits behind NIIT
The Net Investment Income Tax is a 3.8% federal tax under Internal Revenue Code Section 1411. For an individual, it generally applies to the lesser of two amounts: net investment income or modified adjusted gross income above the filing-status threshold. Both channels must be positive before NIIT appears.
The calculator keeps those channels physically separate. The income sieve totals the investment categories and subtracts entered deductions. The threshold bridge measures MAGI above the applicable fixed amount. The smaller channel becomes the NIIT base, which is multiplied by 3.8%.
3.8% x min(net investment income, max($0, MAGI – filing-status threshold)).
Federal NIIT thresholds by filing status
The statutory threshold is $200,000 for single and head-of-household filers, $250,000 for married filing jointly and qualifying surviving spouses, and $125,000 for married filing separately. These thresholds are not regular income-tax brackets and are not the 0%, 15% or 20% long-term capital-gain boundaries.
| Filing status | MAGI threshold |
|---|---|
| Single | $200,000 |
| Head of household | $200,000 |
| Married filing jointly | $250,000 |
| Qualifying surviving spouse | $250,000 |
| Married filing separately | $125,000 |
Unlike many indexed tax amounts, the individual NIIT thresholds have remained fixed. Inflation does not create an automatic annual increase. Estates and trusts use a different threshold tied to the highest tax-bracket starting point and are outside this individual calculator.
Building modified adjusted gross income
For many U.S. resident taxpayers, NIIT modified adjusted gross income begins with Form 1040 adjusted gross income and adds back certain foreign earned income exclusions and related adjustments. It is not automatically the same as taxable income. The standard or itemized deduction generally does not reduce MAGI because those deductions come later.
A taxpayer with no relevant foreign earned income exclusion may find that MAGI equals AGI, but that should be verified rather than assumed. Controlled foreign corporation, passive foreign investment company and expatriate rules can require more specialized modifications. Use Form 8960 instructions when international items are present.
MAGI includes both investment and noninvestment income. Wages can push MAGI over the threshold even though wages themselves are not net investment income. That is why entering only dividends and gains as MAGI would understate the second channel.
Investment income commonly included in the sieve
Net investment income generally includes taxable interest, dividends, annuities, royalties, rents, income from passive activities, income from a trade or business of trading financial instruments or commodities, and net gain from property dispositions to the extent the gain is not otherwise excluded.
Capital gain from stocks, funds, investment real estate and other property can enter the calculation. A gain excluded from regular income, such as qualifying gain on the sale of a principal residence within the Section 121 exclusion, is generally not included merely for NIIT. Gain above the exclusion can be relevant.
Rental income is not automatically included or excluded. Material participation, real-estate-professional status, self-rental rules and grouping elections can affect whether an activity is passive and how its income or gain is treated. The category input assumes the user has already determined the amount included for NIIT.
Income that is generally outside net investment income
Wages, unemployment compensation, Social Security benefits, alimony, and income from a nonpassive trade or business that is not a trading business are generally not NII simply because they raise MAGI. Tax-exempt interest is generally outside NII. Distributions from qualified retirement plans and IRAs are generally excluded from NII, although they can increase MAGI and thereby expand the threshold-excess channel.
Self-employment income is generally subject to self-employment tax rules rather than automatically becoming NII. A business owner’s participation and the nature of the business matter. The exclusion of an income item from the NII channel does not mean it is exempt from regular federal income tax.
Properly allocable deductions
Net investment income is gross investment income and gain reduced by deductions properly allocable to that income, subject to Form 8960 rules. Potential items can include investment interest expense, state and local income tax allocable to investment income, rental or royalty expenses, and expenses associated with a trade or business included in NII.
The amount is not simply every cost appearing on an investment statement. Itemized-deduction limitations, capitalization rules, suspended passive losses, investment-interest limits and allocation methods can change what is currently allowed. Enter a positive deduction amount; the sieve subtracts it once.
Capital losses are generally reflected in the net gain amount under the tax rules rather than entered again as an allocable deduction. Duplicating a loss in both inputs would understate NII.
Worked lesser-of example
Assume a single filer has $260,000 of NIIT MAGI. The MAGI-excess channel is $60,000 because the threshold is $200,000. Investment streams include $12,000 of interest and dividends, $30,000 of net gain and $8,000 of rents, for $50,000 before deductions. Properly allocable deductions of $2,000 leave $48,000 of net investment income.
The lesser of $48,000 and $60,000 is $48,000. Applying 3.8% produces NIIT of $1,824. The unused portion of the MAGI-excess channel is $12,000. It does not create tax without more net investment income.
If MAGI instead were $230,000, the excess channel would be $30,000. The same $48,000 NII would produce a $30,000 base and $1,140 of NIIT. The unused NII would be $18,000.
Capital gains can face two federal layers
A long-term capital gain can owe regular preferential-rate tax and NIIT at the same time. The NIIT rate does not replace the 0%, 15% or 20% capital-gain rate. It is an additional calculation using MAGI and NII. A gain in the regular 0% bracket can still contribute to NIIT in an unusual overall return, while a high-income taxpayer with no NII can have no NIIT.
A complete return should also evaluate state tax and estimated-payment obligations.
Business, rental and real-estate sale cautions
Passive activity rules are central to NIIT. A taxpayer who materially participates in an operating business may exclude qualifying business income from NII, while a passive investor may include it. Trading financial instruments or commodities has a specific inclusion rule even when participation is active.
Real-estate professionals must meet statutory tests, and material participation is determined by activity. Merely holding a license or calling oneself a professional is not enough. Grouping choices can change the analysis and may have long-term consequences.
On disposition, suspended passive losses, depreciation recapture, Section 1231 character and the gain attributable to an activity can all affect Form 8960. Entering gross sales price instead of net included gain is incorrect.
Planning moves and their tradeoffs
Taxpayers sometimes consider spreading gains across years, harvesting losses, increasing deductible retirement contributions, donating appreciated property or completing an installment sale. Each move affects investment risk, cash flow, regular tax and other return items, not just NIIT. Installment treatment can also have special exceptions and does not necessarily avoid the tax.
Municipal-bond interest is generally outside NII and MAGI for this purpose, but investment merit, credit risk and state treatment matter. A retirement distribution is generally outside NII but can raise MAGI and therefore expose existing NII. Roth conversions can have the same threshold-channel effect even though conversion income itself is not investment income.
Run before-and-after scenarios with a full return projection. NIIT savings should never be counted twice as a reduction to the regular capital-gain rate.
Form 8960 records to assemble
- Form 1040 AGI and any required foreign-income modifications.
- Forms 1099-INT, 1099-DIV and 1099-B for taxable investment streams.
- Schedule D net gains and the basis records supporting them.
- Schedule E rental, royalty, partnership and S corporation amounts.
- Material-participation and grouping records for business activities.
- Investment interest, state-tax and expense allocations permitted by the form.
- Principal-residence exclusion and other gain-exclusion documentation.
Frequently asked questions
Is NIIT charged on all investment income once MAGI crosses the threshold?
Not necessarily. The tax applies to the lesser of net investment income or MAGI above the threshold, so only the smaller channel is exposed.
Are wages subject to the 3.8% NIIT?
Wages are generally not NII, but they increase MAGI and can cause investment income to become exposed. Additional Medicare Tax is a separate wage and self-employment tax.
Are IRA withdrawals net investment income?
Qualified-plan and IRA distributions are generally excluded from NII, but taxable distributions can increase MAGI and the amount above the threshold.
Does the standard deduction reduce NIIT MAGI?
Generally no. MAGI begins with adjusted gross income, while the standard or itemized deduction is used later to determine taxable income.
Is the $200,000 threshold indexed for inflation?
No automatic inflation adjustment applies to the individual statutory NIIT thresholds shown here.
References
- IRS Net Investment Income Tax page – threshold, included-income and general calculation overview.
- IRS About Form 8960 – current form and instructions for individuals, estates and trusts.
- IRS Topic No. 559, Net Investment Income Tax – concise federal guidance on the 3.8% tax.
- IRS Revenue Ruling 2014-1 – application of Section 1411 to certain income and deductions.
This educational calculator is not tax, legal or investment advice. Classify activities and deductions under the current Form 8960 instructions before filing.