2026 NIIT Net Investment Income Calculator

Background.

This 2026 niit net investment income page is built to apply the 3.8 percent NIIT to the lesser of net investment income and MAGI excess. NIIT is a separate tax with a dual cap, so high investment income alone is insufficient when modified AGI does not exceed the filing threshold. The implemented convention is “NIIT = 3.8% × min(net investment income, max(MAGI − filing threshold, 0)).”

The editable entries are net investment income, modified adjusted gross income, applicable magi threshold, niit rate. Use values from the document or measurement that governs this 2026 niit net investment income question; the defaults are only the worked fixture below. Filing-status selection, excluded trade income, deductions allocable to investments and disposition exceptions remain outside scope. If that 2026 niit net investment income condition is not true, choose a calculation that models the missing convention.

IRS Questions and Answers on the Net Investment Income Tax; 3.8% rate and statutory thresholds documents the convention or governing rule used here. The 2026 niit net investment income output is a transparent scenario under those facts: it does not manufacture an unentered market price, professional determination, carrier quote, legal eligibility finding or locally adopted code value.

What is 2026 niit net investment income calculator?

2026 NIIT Net Investment Income is the relationship behind this decision: nIIT is a separate tax with a dual cap, so high investment income alone is insufficient when modified AGI does not exceed the filing threshold. On this page it means NIIT = 3.8% × min(net investment income, max(MAGI − filing threshold, 0)). Filing-status selection, excluded trade income, deductions allocable to investments and disposition exceptions remain outside scope; that is the line between the reported quantity and a broader tax analysis.

How to use this calculator.

1. 01Confirm that “NIIT = 3.8% × min(net investment income, max(MAGI − filing threshold, 0))” matches the 2026 niit net investment income convention you need.
2. 02Replace the fixture values for net investment income, modified adjusted gross income, applicable magi threshold, niit rate with dated values from the governing record.
3. 03Keep all currencies, measurement units and time periods on the same basis before calculating.
4. 04Read net investment income tax together with this boundary: Filing-status selection, excluded trade income, deductions allocable to investments and disposition exceptions remain outside scope.

The formula.

The calculation uses NIIT = 3.8% × min(net investment income, max(MAGI − filing threshold, 0)). In this 2026 niit net investment income model, the entered terms are net investment income, modified adjusted gross income, applicable magi threshold, niit rate. NIIT is a separate tax with a dual cap, so high investment income alone is insufficient when modified AGI does not exceed the filing threshold, which is why the relationship is presented under this name rather than as a universal alternative. Filing-status selection, excluded trade income, deductions allocable to investments and disposition exceptions remain outside scope. Calculations keep full decimal precision through the relationship and round only the returned display values.

A worked example.

Frequently asked questions.

References& sources.

1. [1]IRS Questions and Answers on the Net Investment Income Tax; 3.8% rate and statutory thresholds. Retrieved 2026-08-07. access: open unless marked otherwise.
2. [2]U.S. Internal Revenue Service. About Form 8960, Net Investment Income Tax. Retrieved 2026-08-07. independence: primary; access: open.
3. [3]U.S. Internal Revenue Service. Topic no. 559, Net investment income tax. Retrieved 2026-08-07. independence: primary; access: open.