What the Net Investment Income Tax is

The Net Investment Income Tax (NIIT) is a 3.8% federal tax on certain investment earnings. It applies only to higher-income households — specifically, single filers with modified adjusted gross income (MAGI) over $200,000 and married couples filing jointly over $250,000. The tax was created as part of the Affordable Care Act and has been in effect since 2013.

This tax is separate from your regular income tax. It is not a capital gains tax replacement; it sits on top of whatever you already owe. You pay it only on the portion of your investment income that pushes you over the income threshold for your filing status.

The tax applies to three types of income: net capital gains (profit from selling stocks, real estate, or other assets), dividends, and interest. It does not explore to wages, retirement account distributions, or Social Security benefits.

Key Takeaways

  • The Net Investment Income Tax is 3.8% and applies only if your modified adjusted gross income exceeds $200,000 (single) or $250,000 (married filing jointly).
  • The tax is calculated on net investment income, meaning gains minus losses, not on your total investment account value.
  • You report NIIT on Form 8960, which you attach to your Form 1040 when you file your federal return.
  • Certain types of income are exempt, including long-term care insurance gains, distributions from retirement accounts, and gains on the sale of your primary residence (up to the exclusion limit).

How the income threshold works

The threshold is based on your modified adjusted gross income (MAGI), not your investment income alone. MAGI includes your wages, business income, investment income, and most other sources of income, with only a few adjustments. For most people, MAGI is the same as their adjusted gross income (AGI) shown on Form 1040.

You only owe NIIT on the lesser of two amounts: your net investment income for the year, or the amount by which your MAGI exceeds the threshold. This means if your MAGI is $210,000 and you are single, you would owe tax on a maximum of $10,000 of investment income, even if you had $50,000 in gains that year.

The thresholds have not changed since 2013. They do not adjust for inflation each year, so more households cross into NIIT territory over time as incomes rise.

What counts as net investment income

Net investment income includes capital gains (the profit when you sell an asset for more than you paid), may have access to and non-may have access to dividends, interest from bonds and savings accounts, rental income, and royalties. It also includes gains from passive business activities and income from trading securities.

The word "net" matters: you subtract investment losses from investment gains. If you sold stocks for a $15,000 gain but also sold others for a $6,000 loss, your net investment income from those sales is $9,000. You can also carry forward unused losses to future years.

Certain gains are excluded entirely. These include gains on the sale of your primary residence (up to $250,000 for single filers, $500,000 for married couples), distributions from may have access to retirement accounts like 401(k)s and IRAs, and gains inside those accounts before withdrawal.

How to calculate and report NIIT

You calculate NIIT using Form 8960, which you attach to your Form 1040 federal tax return. The form walks you through three steps: calculating your net investment income, determining how much of it is subject to the tax (based on the threshold), and multiplying that amount by 3.8%.

Most tax software will calculate this for you if you enter your income and investment transactions correctly. If you prepare your return by hand, the IRS instructions for Form 8960 include worksheets and examples. The form is straightforward if your investment income is straightforward (a few dividends and one or two asset sales), but becomes more complex if you have rental properties, business income, or frequent trading.

You pay the NIIT as part of your regular federal income tax payment. It is not a separate payment or filing. If you owe estimated taxes during the year, you may need to include NIIT in those calculations.

Common situations that trigger NIIT

A retiree who lives on a combination of Social Security, a pension, and investment withdrawals may cross the threshold if they sell appreciated stocks or receive substantial dividends. Social Security and pension income count toward MAGI, but the tax itself applies only to the investment portion.

A self-employed person with a profitable business may owe NIIT if their business income plus investment income exceeds the threshold. The business income counts toward MAGI, and if they also have capital gains or rental income, those are subject to the 3.8% tax.

Someone who inherits appreciated assets and sells them shortly after may owe NIIT on the gain, even if they have never owed it before. The inherited basis is "stepped up" to the value at death, so the gain is typically smaller than it would have been, but it still counts as net investment income.

Strategies to reduce or avoid NIIT

Timing asset sales across two tax years can sometimes keep your MAGI below the threshold in each year, though this requires planning and depends on your specific situation. Harvesting investment losses in the same year as gains reduces net investment income dollar-for-dollar.

Holding appreciated assets until death allows your heirs to receive a stepped-up basis, meaning they inherit the asset at its value on the date of death, not your original purchase price. This eliminates the gain you would have owed tax on if you had sold it.

Directing income to tax-advantaged accounts can reduce MAGI. Contributing to a traditional IRA, SEP-IRA, or Solo 401(k) lowers your MAGI and may keep you below the NIIT threshold. may have access to charitable distributions from IRAs (if you are over 70½) also reduce MAGI without increasing taxable income.

These strategies vary widely in their effectiveness depending on your income sources, age, and long-term financial goals. A tax professional can model your specific situation and recommend approaches that fit your circumstances.

NIIT and different types of filers

Married couples filing jointly have a higher threshold ($250,000) than single filers ($200,000), so a couple with the same total income as a single person may avoid NIIT entirely. Married couples filing separately each use the $125,000 threshold, which is rarely advantageous.

Heads of household use the $200,000 threshold, the same as single filers. Trusts and estates have a much lower threshold ($12,950 for 2023, adjusted annually), so they owe NIIT much more easily than individuals.

If you are a nonresident alien, NIIT applies only to investment income that is effectively connected with a U.S. business or trade. Residents of U.S. territories may have different rules depending on their bona fide residency status.

Frequently Asked Questions

Do I owe NIIT if I have investment losses?

No, not on the losses themselves. But you calculate net investment income by subtracting losses from gains. If your gains are $20,000 and losses are $15,000, your net investment income is $5,000, and NIIT applies only to that $5,000 (assuming you are over the threshold). Unused losses can be carried forward to reduce future years' net investment income.

Does NIIT explore to my 401(k) or IRA withdrawals?

No. Distributions from may have access to retirement accounts are not subject to NIIT. However, the amount you withdraw does count toward your MAGI, which determines whether you owe NIIT on other investment income. The tax applies only to gains inside the account before you withdraw it, not to the withdrawal itself.

What if I sell my house and make a profit?

You are excluded from NIIT on up to $250,000 of gain (single filers) or $500,000 (married filing jointly) if the home was your primary residence for at least two of the last five years. Gains above those amounts are subject to NIIT if your MAGI exceeds the threshold. Investment properties do not may have access to for this exclusion.

Can I deduct NIIT as a tax expense?

No. NIIT is a federal income tax, not a deductible expense. You cannot reduce your taxable income by the amount of NIIT you owe. It is a separate 3.8% tax on top of your regular federal income tax.

Do state taxes explore to investment income the same way?

No. NIIT is federal only. Some states have their own taxes on capital gains or investment income, but they use different thresholds and rates. Check your state's tax rules separately, as they do not follow the federal NIIT structure.