Net Investment Income Tax Threshold Calculation Calculator

What This Calculator Does and Why It Matters

The Net Investment Income Tax, commonly called NIIT, is a 3.8% surtax that applies to certain investment income earned by higher-income taxpayers. It was introduced as part of the Affordable Care Act and applies to individuals, estates, and trusts whose income crosses specific thresholds set by the IRS.

This free calculator helps you determine whether your income exceeds the NIIT threshold for your filing status, how much of your investment income is subject to the 3.8% tax, and exactly what you owe. It uses the same IRS logic outlined in Form 8960, so your estimate is based on the correct legal calculation — not a rough guess.

If you are also evaluating your broader tax picture, the net investment income tax threshold calculation calculator works well alongside tools like the capital loss carryover deduction calculator to model how losses might reduce your taxable investment income.

How to Use This Calculator

Step-by-Step Instructions

1. Select your filing status from the dropdown — Single, Married Filing Jointly, Married Filing Separately, or Head of Household.
2. Enter your total wages, salary, and other ordinary income for the year.
3. Enter your net investment income — this includes interest, dividends, capital gains, rental income, and passive income, minus any deductible expenses directly tied to earning that income.
4. Click Calculate. The tool will show your MAGI, whether it exceeds the threshold, and your estimated NIIT liability.
5. Use Reset to clear all fields and run a new scenario.

The Formula Explained

Breaking Down the Formula

The IRS calculates NIIT on the lesser of two amounts: your net investment income, or the amount by which your Modified Adjusted Gross Income (MAGI) exceeds the statutory threshold for your filing status. The thresholds as of 2026 are $200,000 for single filers, $250,000 for married filing jointly, $125,000 for married filing separately, and $200,000 for head of household.

The formula is: NIIT = 3.8% × min(NII, MAGI − Threshold). This ensures you are only taxed on the portion of investment income that falls above the income cutoff, not your full investment income in every case. You can read more about how the IRS defines these terms on the IRS Topic 559 page.

Example Calculation with Real Numbers

Suppose you file as single with $190,000 in wages and $40,000 in net investment income. Your MAGI is $230,000. The threshold is $200,000, so your MAGI exceeds it by $30,000. The lesser of $40,000 (NII) and $30,000 (MAGI above threshold) is $30,000. Your NIIT would be 3.8% of $30,000, which equals $1,140.

When Would You Use This

Real Life Use Cases

This calculator is most useful during tax planning — ideally mid-year when you can still make adjustments. It is also valuable when you are considering a large capital gain event like selling a rental property, a business stake, or a significant stock position. Knowing your potential NIIT exposure ahead of time lets you consider strategies to reduce it.

Investors who are close to the threshold may also use it to model whether contributing more to a traditional IRA or 401(k) could lower their MAGI enough to reduce or eliminate NIIT. The solo 401k contribution calculator can help you model exactly how much a retirement contribution could reduce your MAGI.

Specific Example Scenario

A married couple filing jointly has $240,000 in combined salary and $35,000 in dividend and capital gain income. Their MAGI is $275,000. Since the threshold is $250,000, they exceed it by $25,000. The lesser of $35,000 and $25,000 is $25,000. Their NIIT is $950. If they increase 401(k) contributions by $25,000, their MAGI drops to $250,000 — right at the threshold — and NIIT drops to zero.

Tips for Getting Accurate Results

Know What Counts as Net Investment Income

Not all investment-related income qualifies as NII. Wages, self-employment income, IRA distributions, and Social Security do not count. NII includes interest, ordinary dividends, capital gains, rental income (if not from an active trade or business), and income from passive activities. Using the wrong number here is the most common mistake people make when estimating NIIT.

Subtract Allowable Deductions From Your NII

Net investment income is calculated after deducting expenses directly allocable to earning it. Investment advisory fees, rental expenses, and state and local taxes on investment income may all reduce your NII. Using the gross figure instead of the net will overstate your NIIT liability. Check IRS Form 8960 instructions for the full list of allowable deductions.

Run Multiple Scenarios Before Year End

NIIT planning works best when done proactively. If you are close to the threshold, small changes like deferring a capital gain sale, harvesting losses, or maximizing retirement contributions can shift your outcome meaningfully. Use this calculator to test different combinations of income and deductions before you finalize any financial decisions. The crypto tax loss harvesting calculator is one useful companion tool if investment losses are part of your strategy.

Frequently Asked Questions

What is the Net Investment Income Tax?

The Net Investment Income Tax is a 3.8% surtax that applies to investment income for taxpayers whose Modified Adjusted Gross Income exceeds certain thresholds. It was established under the Affordable Care Act and applies to individuals, estates, and trusts. It is separate from regular income tax and is reported on IRS Form 8960.

What income is subject to NIIT?

Net investment income subject to NIIT includes interest, dividends, capital gains, rental and royalty income, and income from passive activities or trading in financial instruments or commodities. Wages, self-employment income, IRA or retirement plan distributions, and Social Security benefits are not included.

What are the NIIT income thresholds for 2026?

The thresholds are $200,000 for single filers and heads of household, $250,000 for married filing jointly, and $125,000 for married filing separately. These thresholds are not adjusted for inflation, so they have remained the same since the tax was introduced in 2013.

Is NIIT the same as the Medicare surtax?

They are related but separate. The 3.8% NIIT is sometimes called the Medicare surtax because the revenue goes toward Medicare funding. There is also a separate 0.9% Additional Medicare Tax on earned income above similar thresholds. The NIIT applies to investment income, while the 0.9% tax applies to wages and self-employment income.

Can I reduce my NIIT by making retirement contributions?

Yes. Traditional IRA, 401(k), SEP IRA, and similar pre-tax retirement contributions reduce your MAGI, which can bring it below the NIIT threshold or reduce the amount subject to the tax. This is one of the most common and effective planning strategies for higher-income earners who are close to the threshold.

Does NIIT apply to rental income?

It depends. Rental income from passive activities is generally subject to NIIT. However, if you are a real estate professional who materially participates in rental activities, that income may not be treated as passive and therefore may not be subject to NIIT. The distinction depends on time spent and involvement, which is a fact-specific determination.

Do I have to pay estimated taxes on NIIT?

Yes. If you expect to owe NIIT, you should include it in your quarterly estimated tax payments to avoid underpayment penalties. The IRS treats NIIT as part of your regular income tax for estimated payment purposes. Missing estimated payments can result in additional penalty charges at tax time.

Where do I report NIIT on my tax return?

NIIT is calculated and reported on IRS Form 8960, which is filed with your Form 1040. The final NIIT amount flows to Schedule 2 of Form 1040 as an additional tax. Most major tax preparation software will complete Form 8960 automatically when it detects that your income exceeds the applicable threshold.

Conclusion

The Net Investment Income Tax is a meaningful surtax that can add thousands of dollars to your annual tax bill if you are not prepared for it. Because the thresholds have never been adjusted for inflation, more taxpayers are affected by NIIT each year as incomes rise.

Use this calculator early in the year to get ahead of the liability. If the result shows a significant exposure, you still have time to consider strategies that may reduce it. Run different scenarios, consult with a tax advisor, and keep more of your investment returns working for you.