A second tax on the same income
The net investment income tax applies at a flat rate on the lesser of net investment income for the year, or the excess of modified adjusted gross income over a threshold.
It sits on top of ordinary income tax and capital gains tax rather than replacing either. For a taxpayer at the top bracket it raises the effective rate on the affected income accordingly, and it is frequently omitted from illustrations that quote a headline rate.
What counts, and what does not
| Generally included | Generally excluded |
|---|---|
| Interest, dividends, annuities, royalties | Wages and self-employment income, which bear their own employment taxes instead |
| Capital gains, including on the sale of investment property | Distributions from qualified retirement plans and IRAs |
| Rents, other than from a non-passive trade or business | Income from a trade or business in which the taxpayer materially participates |
| Income from a passive trade or business | Tax-exempt interest |
| Income from trading in financial instruments or commodities | Gain excluded from income, such as the excluded portion of a principal residence gain |
The definition is net, and properly allocable deductions reduce it. That is a point worth raising with a preparer, because the allocation is not automatic and is sometimes not made.
Where material participation decides the answer
The most consequential line runs between active and passive business income, and it is the same line drawn by the passive activity rules.
Income from a trade or business in which the taxpayer materially participates is generally outside the surtax. The identical business, with the identical income, produces income that is inside the surtax if the taxpayer does not materially participate.
That makes the material participation analysis load-bearing twice: once for whether losses are usable, and again for whether profits bear an additional layer of tax. An owner who has withdrawn from day-to-day involvement may have moved from one side of that line to the other without anyone raising it.
What actually reduces it
The threshold test means the surtax can be reduced either by reducing net investment income or by reducing modified adjusted gross income, since the tax applies to the lesser of the two.
- 01Where material participation is genuinely achievable and not currently established, it changes the characterization of business income prospectively. It is a facts question and not a labelling exercise.
- 02Realisation timing on capital gains affects both measures in the same year, which makes it the most direct lever available.
- 03Municipal interest is outside the base entirely, which is part of the comparison when the alternative is taxable interest.
- 04Charitable and other deductions that reduce modified adjusted gross income can reduce the surtax indirectly even where net investment income is unchanged.
- 05Trusts face the same surtax at a compressed threshold, which is a further reason the retain-or-distribute decision is made annually rather than by habit.
General information only. This article describes law and practice as we understand them at the time of writing. It is not tax, legal, accounting, or investment advice, it does not consider your circumstances, and it does not create an advisor-client or attorney-client relationship. Odyssey Strategic Advisors LLC is not a law firm and is not a CPA firm. Confirm any position with your own tax professional before acting on it. See our disclosures.