Net Investment Income Tax Calculator (US)

This Net Investment Income Tax calculator estimates the 3.8% NIIT based on investment income and modified adjusted gross income. It is useful for investors whose income may exceed the NIIT thresholds.

Net investment income can include interest, dividends, capital gains, rental income, royalties, and certain passive income. The tax generally applies to the lesser of net investment income or the amount by which MAGI exceeds the threshold.

If net investment income is $30,000 and MAGI exceeds the relevant threshold by $12,000, the simplified NIIT base may be $12,000. At 3.8%, the estimated NIIT is $456.

If investment income is lower than the MAGI excess, the tax is based on the lower investment income figure instead.

NIIT can matter when selling appreciated investments, receiving large dividends, selling property, or recognizing passive income.

Use the estimate before year-end planning, then confirm exact treatment with IRS rules or a tax professional.

Use this calculator for the 3.8% Net Investment Income Tax when you already know net investment income, modified adjusted gross income, and filing status.

The component compares net investment income with MAGI above the selected filing-status threshold, then taxes the lesser amount.

Use capital gains tax us when the starting question is gain on a sale, and dividend tax when the question is qualified versus ordinary dividend tax.

Use rental income tax before this page if rental income, expenses, and depreciation need to be estimated first.

Label saved scenarios with MAGI, net investment income, and filing status because those three inputs decide whether NIIT appears at all.

Applying 3.8% to total income instead of the lesser of net investment income or excess MAGI.

Entering gross investment receipts as net investment income without subtracting the deductions or expenses you intend to include.

Forgetting that the calculator does not decide whether a rental, business, trust, or estate item is included in net investment income.

Using this page as a capital gains tax calculator. It only estimates the extra NIIT layer after net investment income and MAGI are known.

Assuming the thresholds are enough for filing. NIIT treatment can depend on detailed income classification and current IRS rules.

Example: enter $50,000 of net investment income and $275,000 of MAGI with single filing status.

The calculator compares the filing-status threshold with MAGI, finds the excess MAGI amount, then uses the lesser of excess MAGI and net investment income as the taxable NIIT base.

At the fixed 3.8% rate in the component, the result shows estimated NIIT and the base used.

Change MAGI and investment income separately so you can see whether the limiting factor is the threshold side or the investment-income side.

Use capital gains tax us to estimate gain and ordinary capital-gains tax before checking whether NIIT may add another layer.

Use dividend tax for qualified and non-qualified dividend tax, then include the relevant net investment income here if needed.

Use rental income tax for rental taxable income assumptions before deciding whether rental income belongs in the NIIT input.

Use federal income tax or tax software when you need MAGI rather than a manual estimate.

Check whether the filing status and MAGI threshold match the tax year being modelled.

Check whether the investment income entered is net investment income for NIIT purposes, not just brokerage income before adjustments.

Check whether rental, business, trust, estate, or passive-activity rules need professional review before filing.

Rerun this NIIT calculator when MAGI, filing status, dividends, interest, capital gains, rental income, or other investment income changes.

Recheck before large asset sales or year-end income events if MAGI is close to a threshold.

If this estimate differs from tax software, trace MAGI, net investment income, filing status, and excluded income separately.