Introduction
Plenty of U.S. taxpayers assume that once their income crosses a threshold, the Net Investment Income Tax (NIIT) hits every dollar of investment income. It doesn't. Form 8960 runs a separate calculation, and the tax lands only on the lesser of two amounts.
A return filed in 2026 covers tax year 2025 and uses the final 2025 Form 8960. The 2026 form is still a draft, not for filing.
Line references in this guide match the final 2025 documents. Check the IRS pages again before you file.
This guide covers who needs Form 8960, what counts as net investment income, how line 9b works, and what U.S. taxpayers living in Australia should review.
Key Takeaways
- Form 8960 calculates NIIT only, not regular income tax on every income type.
- NIIT is 3.8% of the lesser of net investment income or MAGI above your threshold.
- Individual thresholds are fixed at $200,000, $250,000 or $125,000 by filing status.
- FEIE add-backs, PFICs, foreign taxes and exchange rates are the main risk points for Australian filers.
What Is Form 8960 and Who Must File?
Under Internal Revenue Code section 1411, the Net Investment Income Tax (NIIT) applies to individuals, estates and trusts. You calculate that tax on Form 8960.
- Net investment income (NII): investment income and net gains, less properly allocable deductions.
- Adjusted gross income (AGI): gross income from all sources, less specified adjustments.
- Modified adjusted gross income (MAGI): generally AGI, with adjustments for items such as foreign earned income exclusions and certain CFC or PFIC interests.
Who must file Form 8960?
The IRS instructions require you to attach the form when your MAGI exceeds your threshold. Positive NII is not required to file. You owe the tax only when MAGI exceeds the threshold and you have NII.
Filing-status thresholds for individuals
| Filing status | MAGI threshold |
|---|---|
| Single or head of household | $200,000 |
| Married filing jointly or qualifying surviving spouse | $250,000 |
| Married filing separately | $125,000 |
These amounts are not indexed for inflation.
Estates and trusts
Estates and trusts pay 3.8% of the lesser of undistributed NII or AGI above the start of the highest trust bracket. That figure is $15,650 for 2025 and $16,000 for 2026. Estates and trusts complete lines 18 to 21. Distributions to beneficiaries shift where the income is taxed.
Filing Form 8960 versus paying NIIT
For example, a single filer has $210,000 of wages and no investment income. MAGI exceeds $200,000, so you must attach the form. NII is zero, so NIIT is zero.
What Counts as Net Investment Income, and What Can Reduce It?
Net investment income and MAGI follow separate exclusion rules. An item can be excluded from NII and still raise your MAGI.
| Generally included | Generally excluded |
|---|---|
| Interest, dividends, royalties, rents | Wages |
| Non-qualified annuities | Social Security |
| Passive business income | Tax-exempt interest |
| Trading in financial instruments or commodities | Nonpassive operating-business income |
| Net capital gains | Qualified retirement-plan distributions (401, 403, 408, 408A, 457(b)) |
Gain on a main home excluded under section 121 is also excluded from NII. Only the excess gain enters the calculation.
Passive, active, rental and business income
Passive-activity status and material participation decide whether rental and business income is NII. Real-estate-professional status alone does not establish material participation.
The rental safe harbour needs that status plus more than 500 hours in the activity that year, or in any 5 of the prior 10 years. Missing the safe harbour does not automatically make the income NII.
Special investment and foreign-income categories
- Foreign dividends, interest and rents generally fall in the same categories, because U.S. citizens and resident aliens report worldwide income
- Death benefits and inherited property are generally excluded; later interest, dividends and rents on that property are taxable
- CFC and PFIC income needs fact-specific analysis (see the Australia section)
How to Calculate NIIT and Complete Form 8960
The formula is 3.8% x the lesser of NII or MAGI above your threshold. Work through it in order:
- Determine MAGI.
- Total gross investment income.
- Subtract properly allocable deductions and modifications.
- Compare NII with the excess of MAGI over your threshold.
- Apply 3.8% to the lesser amount.
The IRS benchmark: a single filer with $180,000 of wages and $90,000 of passive partnership income has MAGI of $270,000. NIIT is $2,660, based on the $70,000 excess, not all $90,000 of NII.
Part I: Investment income
Part I gathers interest, dividends, annuities, rents, royalties, passive business income and net gains, plus foreign-entity adjustments. Confirm line numbers against the final form for your year.
Part II: Investment expenses and modifications
Part II covers investment interest, rental and royalty expenses, and other deductions the NIIT rules allow. Expenses must be properly allocable to investment income and backed by records.
Understanding line 9b
Line 9b covers state, local and foreign income taxes attributable to NII. The instructions allow any reasonable allocation method. Two warnings:
- A foreign income tax deduction is unavailable if you took a credit for any portion of that year's foreign income taxes.
- A foreign tax credit and an allocable deduction are different things. Do not count the same tax twice.
Part III: Tax computation and reporting
Individuals use lines 13 to 17. On the 2025 forms, line 17 transfers to Schedule 2 (Form 1040), line 12. Estates and trusts use lines 18 to 21, with line 21 going to Form 1041, Schedule G, line 5. Verify destinations on the form for your year.
Records and filing workflow
Form 8960 attaches to your return and follows its deadline. Keep:
- Brokerage statements, dividend and interest records
- Sale dates and basis
- Rental records
- Foreign tax documents and exchange rates
- Forms 2555, 1116, 8621, 5471 and K-1s
- Retirement statements
How Form 8960 Works for U.S. Taxpayers in Australia
Australian interest, dividends, managed-fund income, rent and capital gains all need review for both NII and MAGI. Living outside the United States also changes your filing timeline. Eligible citizens and residents abroad get an automatic two-month extension to 15 June, but interest still runs from the regular payment date.
The Foreign Earned Income Exclusion and MAGI
Excluded foreign earned income is not NII. But MAGI adds back the section 911 exclusion, net of disallowed associated deductions. That can push you over the threshold and expose your other investment income to NIIT.
Foreign-currency conversion
Report in U.S. dollars. The IRS generally uses the rate when an item is received, paid or accrued. It publishes no mandatory rate, but accepts consistently applied, supportable rates. Currency movements can change your U.S. gain on Australian assets even when the Australian-dollar result looks flat.
Foreign tax credits and line 9b
Treasury Regulation 1.1411-1(e) disallows foreign tax credits against NIIT. Article 22(1) of the Australia treaty makes the U.S. credit subject to U.S. law limits, and the 2001 protocol does not change that. Recent court cases (Toulouse, and the 2026 Federal Circuit reversal in Christensen) involved French and Italian treaties, not Australia's.
Australian superannuation, PFICs, CFCs and managed funds
Do not classify these by label.
- Managed funds and ETFs: PFIC status turns on the 75% passive-income or 50% passive-asset tests. Form 8621 is generally filed per PFIC.
- CFCs: Australian companies may trigger Form 5471. That reporting is distinct from the CFC NII computation.
- Section 1411 election: Under Treas. Reg. 1.1411-10, later distributions may enter NII despite an earlier inclusion. The irrevocable paragraph (g) election brings those inclusions into NIIT in the current year.
- Superannuation: Treaty Article 18 does not classify individual arrangements. Have a specialist review your specific plan.
Rev. Proc. 2020-17 offers foreign-trust reporting relief, not an NIIT exemption.
Residency, treaty and nonresident issues
NIIT does not apply to nonresident aliens. Dual-status filers are subject only for the U.S.-resident portion, with no proration of thresholds. Australian residence alone does not decide liability; the full U.S. residency and treaty position must be reviewed.
How to Reduce or Avoid NIIT in 2026
Lawful planning reduces NIIT only by lowering NII or MAGI. Do not make investment decisions purely to avoid NIIT.
Practical steps include:
- Time capital gains. Instalment-sale adjustments apply as payments arrive.
- Harvest losses where appropriate. Capital losses offset included gains.
- Make eligible retirement contributions, which reduce AGI, though NIIT modifications still apply.
- Consider tax-exempt interest, which is excluded from NII.
- Review whether you meet the tests for nonpassive, material participation.
Year-end projections should cover wages, bonuses, business income, Roth conversions, retirement distributions, realised gains, foreign income and currency effects. NIIT follows estimated-tax rules, so adjusted withholding or estimated payments manage underpayment exposure. They do not reduce the liability itself.
If you hold Australian investments, foreign taxes, FEIE, PFICs, CFCs or rentals, VJM Global's U.S.-compliant professionals can support your cross-border tax compliance and Form 8960 calculation.
Frequently Asked Questions
What is the net investment income tax and what is Form 8960 used for?
NIIT is a 3.8% U.S. federal tax on certain investment income of higher-income taxpayers. Form 8960 calculates the amount due. Confirm rules for your tax year with the IRS.
Who has to pay NIIT and who must file Form 8960?
Individuals owe NIIT when MAGI exceeds their threshold and they have NII. You must attach the form when MAGI exceeds the threshold. Estates and trusts use separate undistributed-income rules.
What are the filing thresholds and when must I file?
Thresholds are US$200,000 (single or head of household), US$250,000 (joint or qualifying surviving spouse) and US$125,000 (married filing separately). File the form with your U.S. return, including any extension.
How is NIIT calculated, including line 9b?
NIIT is 3.8% of the lesser of NII or excess MAGI. Line 9b allocates state, local or foreign income taxes to NII. Do not claim a deduction for foreign taxes you credited.
What income is subject to NIIT and what is excluded?
Interest, dividends, rents, royalties, passive income and net gains are generally included. Wages, tax-exempt interest, Social Security and qualified retirement distributions are excluded.
How can I reduce or avoid NIIT in 2026?
Manage NII and MAGI through gain timing, losses, eligible deductions and retirement planning. Report foreign income accurately, and seek professional review for Australian investments.
