Net Investment Income Tax (NIIT) in 2026: How the 3.8% Surtax Hits Investors When MAGI Crosses the $200,000 / $250,000 Threshold — and Why More Households Owe It Every Year

Why 2026 Is a Watershed Year for the 3.8% Net Investment Income Tax

The Net Investment Income Tax (NIIT) is a 3.8 % federal surtax on investment income for higher-income individuals, estates, and trusts. Codified at Internal Revenue Code §1411, it was enacted as part of the Health Care and Education Reconciliation Act of 2010 (Pub. L. 111-152) and took effect on January 1, 2013. Since that date, the dollar thresholds that determine who owes the tax have never been adjusted for inflation: $200,000 for Single and Head-of-Household filers, $250,000 for Married Filing Jointly and Qualifying Widow(er)s, and $125,000 for Married Filing Separately. As a result, every year of inflation pulls more households across these frozen lines without any change in the law itself — a phenomenon known as bracket creep.[1, 16, 15]

Why does 2026 matter specifically? Three reasons converge. First, cumulative consumer-price inflation since the NIIT thresholds were set has eroded their real value substantially — the Bureau of Labor Statistics CPI-U index has risen roughly 38 % from January 2013 through early 2026, meaning that today's $200,000 threshold corresponds to roughly $145,000 in 2013 purchasing power. Second, despite frequent social-media speculation, the One Big Beautiful Bill Act (OBBBA, Pub. L. 119-21, signed July 4, 2025) did not amend §1411. The IRS's official OBBBA provisions page lists no NIIT change, and Cornell's annotated §1411 statute shows only the original 2010 enacting law (Pub. L. 111-152) — the rate, the thresholds, and the rules all remain identical to 2013. Third, OBBBA's temporary expansion of the SALT cap to $40,400 in 2026 with a phaseout starting at $505,000 MAGI changes how state income tax allocable to net investment income is deducted on Form 8960 Line 9b — a quiet but consequential interaction that high-income investors must model.[25, 23, 24, 22]

This guide unpacks how §1411 actually works in 2026 — the lesser-of formula, the precise definition of Modified Adjusted Gross Income (MAGI) under §1411(d), what the three §1411(c) categories of "net investment income" do and do not include, the line-by-line mechanics of Form 8960, the often-overlooked $16,000 trust threshold tied to §1(e), the §469(c)(7) real-estate-professional carve-out, and eight defensible strategies to reduce or eliminate your NIIT exposure. Because every dollar of NIIT compounds into a much larger lost balance over a multi-decade investing horizon, modelling the long-run impact matters: use our compound interest calculator to see how a 3.8 % drag on annual returns compares against a properly NIIT-aware portfolio over 30 years.[1, 10, 27]

How IRC §1411 Actually Works — The Statute, the MAGI Definition, and the Math in Plain English

The core mechanic of NIIT is what tax practitioners call the "lesser-of" rule. Under §1411(a)(1), an individual's NIIT equals 3.8 % multiplied by the lesser of (i) net investment income for the year, or (ii) the excess of MAGI over the applicable threshold. This bilateral test means the tax can never exceed 3.8 % of NII — and it can never apply to a household whose MAGI is at or below the threshold, regardless of how much investment income they earned. A single filer with $300,000 of MAGI and $50,000 of NII pays 3.8 % × min($50,000, $300,000 − $200,000) = 3.8 % × $50,000 = $1,900. A single filer with $300,000 of MAGI but only $30,000 of NII pays 3.8 % × min($30,000, $100,000) = $1,140. The first variable — net investment income — is usually the binding constraint for retirees and dividend-focused investors, while the second variable — MAGI excess — binds for active high-earners with concentrated wage income.[1, 16, 10]

A common — and consequential — error is to confuse §1411 MAGI with the MAGI used for IRA contribution limits, the Premium Tax Credit, or IRMAA Medicare premiums. Each of those uses a different add-back recipe. Under §1411(d), the NIIT MAGI is simply Adjusted Gross Income (Form 1040 Line 11) plus the foreign earned income excluded under §911(a)(1), minus deductions and exclusions disallowed under §911(d)(6). For most U.S.-domestic filers, MAGI for NIIT purposes therefore equals AGI exactly — no additional add-backs for tax-exempt municipal bond interest, no add-back for Social Security excluded portions, and no add-back for IRA contributions. The IRS's NIIT FAQ explicitly confirms this point. Confusing the rules across MAGI definitions is one of the single most common preparer errors on Form 8960.[1, 16, 10]

The threshold table that applies to the 2026 tax year is identical to the table that applied in 2013, in 2018, and in every year between: Single and Head of Household, $200,000; Married Filing Jointly and Qualifying Widow(er), $250,000; Married Filing Separately, $125,000. For estates and non-grantor trusts, however, the threshold is much lower and is updated annually for inflation. Under §1411(a)(2), the trust threshold is the dollar amount at which the highest income tax bracket under §1(e) begins for the tax year — and per Rev. Proc. 2025-32, that figure is $16,000 for 2026. A trust with as little as $20,000 of undistributed investment income can therefore owe NIIT on $4,000 of that income, while an individual with the same investment income would owe nothing if their MAGI is below $200,000. This 12.5×-lower threshold is the single biggest reason DNI distribution planning matters in irrevocable trust administration.[1, 27, 6]

NIIT does not replace the regular income tax on investment income — it stacks on top of it. For long-term capital gains and qualified dividends taxed at the 20 % top federal rate, the effective combined federal rate is 23.8 % (20 % + 3.8 %). For ordinary investment income such as bond interest, non-qualified dividends, and short-term capital gains taxed at the 37 % top federal rate, the effective rate is 40.8 % (37 % + 3.8 %). State income tax — which can exceed 13 % in California, New York, New Jersey, and Oregon — sits on top of these federal rates, pushing combined marginal rates on investment income for top-bracket residents in high-tax states above 50 % in some configurations. The 26 CFR §1.1411 final regulations under T.D. 9644 (effective Dec 2, 2013) implement these rules in granular detail, and the 2025 Form 8960 instructions confirm no changes for 2026.[5, 8, 10]

What Counts as Net Investment Income — The Three §1411(c) Categories

§1411(c)(1) defines net investment income through three categories. Category 1 is gross income from interest, dividends, annuities, royalties, and rents, other than such income derived in the ordinary course of an active (non-passive) trade or business. Most household investment income falls here: bank-account interest, brokered CD interest, taxable bond interest, ordinary dividends, qualified dividends, and rental income from real estate held passively. Royalty income from intellectual property licensing — except where the taxpayer is materially involved in the trade — is also Category 1. Per IRS Publication 550, the rents-and-royalties subset is the most frequent source of audit disputes because the boundary between "active" and "passive" rental activity is fact-intensive.[1, 7, 11, 15]

Category 2 is the net gain (or loss) from the disposition of property held for investment — capital gains realized on the sale of stocks, mutual funds, ETFs, REIT shares, bonds sold before maturity (where market discount accrues), and partnership or S-corporation interests. Importantly, the gain on a sale of a partnership or S-corp interest is included only to the extent of the seller's share of the entity's underlying NII (the 26 CFR §1.1411-7 "deemed-sale" rule). Capital losses can offset capital gains within Category 2 but cannot create a negative number that reduces Categories 1 or 3 below zero. The principal-residence sale exclusion under §121 ($250,000 single, $500,000 joint) flows directly through to NII — so the home-sale gain is reduced by the same exclusion that reduces regular capital-gains tax.[1, 7, 11, 17]

Category 3 picks up income from passive trades or businesses (within the meaning of §469) and from the trade or business of trading in financial instruments or commodities. This is the catch-all that pulls in income that did not appear in Category 1 or 2 because of its business form — for example, the share of K-1 income from a real-estate partnership in which the investor does not materially participate, or the trading-business income of a financial trader who does not qualify for trader-tax-status mark-to-market under §475(f). From the gross income in Categories 1, 2, and 3, taxpayers subtract the deductions properly allocable to that income: investment interest expense (capped by §163(d)), state and local income tax allocable to NII (subject to the §164(b)(6) SALT cap interaction), investment-related advisory and custodial fees (suspended for individuals through 2025 by TCJA and not restored by OBBBA), and the deductible portion of the §1411 trade-or-business losses.[1, 7, 20, 22, 11]

What Does NOT Count Toward NII — Wages, Self-Employment, and the Retirement-Account Lifeline

The single most powerful planning lever in §1411 sits in §1411(c)(5): distributions from qualified retirement plans are explicitly excluded from net investment income. The statute lists six plan categories — §401(a) plans (including 401(k), profit-sharing, defined-benefit, and money-purchase plans), §403(a) annuity plans, §403(b) tax-sheltered annuities, §408 IRAs (Traditional, SEP, SIMPLE, Roth IRA conversions sourced from these), §408A Roth IRAs, and §457(b) governmental deferred-compensation plans — and distributions from any of these are not NII regardless of the underlying investment composition. A retiree taking $80,000 per year from a Traditional 401(k) sees zero NIIT on those distributions, even though the same $80,000 of dividends and interest in a taxable brokerage account would be fully exposed.[1, 13, 16, 15]

Equally important is what else falls outside NII's scope. Wages and salaries (Form W-2 box 1) are not NII. Self-employment income from a non-passive trade — Schedule C net profit, the active partner's share of partnership ordinary income, S-corp wages — is not NII (though SE income is hit by a parallel 0.9 % Additional Medicare Tax under §1401). Social Security benefits, Veterans benefits, and unemployment compensation are not NII. Alimony received under post-2018 divorce decrees is not NII (and is also not in AGI under TCJA reform). Life-insurance death benefits are not NII. And tax-exempt municipal bond interest under §103 is excluded from both NII and MAGI — making munis the cleanest single-issue NIIT-avoidance lever for high-bracket investors.[3, 18, 19, 16]

A subtle wrinkle: an S-corporation distribution to a materially-participating shareholder is excluded from NII under the 26 CFR §1.1411-4 active-trade carve-out, even though the distribution itself looks economically similar to a dividend. The same is true for K-1 ordinary income flowing from a partnership in which the partner materially participates under §469. Material participation is tested separately for each activity using the seven-test framework of 26 CFR §1.469-5T, and the most common test is the 500-hour rule: a partner who logs more than 500 hours per year in the activity is materially participating. For a non-managing limited partner — even one with substantial economic exposure — the same K-1 income is normally Category 3 NII unless one of the other six tests is met.[7, 20, 14]

Bracket Creep — Why More Households Pay NIIT Every Year (and Why OBBBA Did Nothing About It)

When Congress wrote §1411 into law in 2010 with thresholds of $200,000 (Single) and $250,000 (MFJ), those numbers represented roughly the top 2 % of the income distribution. Thirteen years later, the same nominal dollar amounts cover a substantially larger fraction of the population. The Bureau of Labor Statistics CPI-U index — the official measure of consumer price inflation — rose approximately 38 % from January 2013 through early 2026. In real terms, the $200,000 single-filer threshold of 2026 corresponds to about $145,000 of 2013 purchasing power; equivalently, a household whose 2013 income would have left them well below the threshold may now find themselves above it on identical inflation-adjusted earnings. This phenomenon — known as bracket creep — is built into §1411 by design: the statute contains no inflation-indexing provision for the individual thresholds, unlike §1(e) which automatically indexes the trust threshold each year.[25, 26, 1]

The IRS Statistics of Income (SOI) division publishes an annual tabulation of NIIT receipts by adjusted gross income bracket. Each successive release shows the absolute number of returns owing NIIT and the dollar value of receipts climbing — driven not by any change in the law but purely by inflation pulling more households across the frozen lines. Investors approaching retirement, holders of appreciated taxable accounts realizing gains during retirement, and households with concentrated employer-stock compensation are the most common new entrants to the NIIT-paying population. The same pattern affects the parallel §1401(b)(2) Additional Medicare Tax and the §86 Social Security taxation thresholds — none of these statutory amounts adjust for inflation, and all of them touch a growing share of taxpayers each year.[26, 19, 25]

Despite frequent online claims to the contrary, the One Big Beautiful Bill Act of 2025 did not repeal, amend, or modify §1411 in any way. The official IRS "One, Big, Beautiful Bill Provisions" page — which catalogs every OBBBA tax change affecting individuals, families, healthcare, businesses, and tax-exempt entities — contains no NIIT entry. Cornell's annotated §1411 statute lists only the original 2010 enacting law (Pub. L. 111-152, the Health Care and Education Reconciliation Act) under amendment notes; no Pub. L. 119-21 (OBBBA) annotation appears. The 3.8 % rate, the $200,000 / $250,000 / $125,000 thresholds, the §1411(c) categories, and the §1411(c)(5) retirement-plan exception all remain identical to their 2013 form. Any change to NIIT thresholds or rate would require a new Act of Congress; the CBO budget baseline through 2035 assumes no such change.[23, 24, 1]

Form 8960 Line-by-Line — How to Calculate and Report Your NIIT in 2026

NIIT is computed and reported on IRS Form 8960, "Net Investment Income Tax — Individuals, Estates, and Trusts." The form is divided into three numbered parts that mirror the statutory structure: Part I (lines 1-7) aggregates investment income, Part II (lines 9-10) subtracts properly allocable deductions, and Part III (lines 13-21) performs the lesser-of computation and produces the final NIIT figure that flows to Schedule 2 (Form 1040). Individual filers use the individual portion (final NIIT on Line 17); estates and trusts use the estate/trust portion (final NIIT on Line 21). The 2025 instructions, current as of the writing of this guide, contain no structural changes for the 2026 tax year.[9, 10]

Part I — Investment Income. Line 1 reports taxable interest from Form 1040 Schedule B Line 2 (typically populated from 1099-INT and 1099-OID). Line 2 reports ordinary dividends (qualified and non-qualified together) from Schedule B Line 6, sourced from 1099-DIV. Line 3 reports annuity income from non-qualified annuities (qualified-plan annuities are excluded by §1411(c)(5) and never enter this line). Line 4 captures rental real estate, royalties, partnership, S-corp, and trust income — with sub-lines 4a (gross), 4b (adjustment for non-§1411 trade-or-business activity), and 4c (net Line 4 amount). Line 5 reports the net gain or loss from disposition of property, with sub-lines 5a (Form 1040 Schedule D net gain), 5b (gain on non-§1411 active trade), 5c (Section 1411 adjustments), and 5d (combined Line 5 amount). Line 6 captures CFC and PFIC adjustments. Line 7 reports any other modifications to NII. Line 8 sums Lines 1 through 7 — the gross investment income before deductions.[10, 11]

Part II — Investment Expenses. Line 9a reports investment interest expense properly allocable to investment income (the same investment-interest amount allowed under §163(d), capped at investment-income amount). Line 9b reports state, local, and foreign income tax allocable to NII — this is where the OBBBA-modified §164(b)(6) SALT cap interacts: only the portion of state income tax that survives the cap and is allocable to NII can be deducted on Line 9b. Line 9c reports other miscellaneous investment expenses (note: most §212 advisory fees remain suspended through 2025 under TCJA and are unavailable for individual filers, though estates and trusts may still deduct them). Line 10 sums Lines 9a through 9c — total deductions properly allocable to NII. Line 11 carries forward the gross NII before deductions; Line 12 subtracts Line 10 to produce net investment income, the value that enters the lesser-of test in Part III.[10, 22, 7]

Part III — Tax Computation. For individuals: Line 13 reports modified adjusted gross income (AGI from Form 1040 Line 11 plus the §911(a)(1) foreign earned income add-back). Line 14 reports the threshold ($200,000 Single/HoH, $250,000 MFJ/QW, $125,000 MFS). Line 15 computes Line 13 minus Line 14 (the MAGI excess; if negative, NIIT is zero). Line 16 selects the lesser of Line 12 (NII) and Line 15 (MAGI excess). Line 17 applies the 3.8 % rate to Line 16 — this is the NIIT. For estates and trusts, lines 18a–c handle the same logic with the §1(e) trust threshold ($16,000 for 2026), and Line 21 produces the trust/estate NIIT. The most common preparer errors are: (a) failing to add back §911(a)(1) excluded foreign earnings on Line 13; (b) forgetting that capital losses cannot drive Line 12 negative for NIIT purposes (the floor is zero); and (c) incorrect SALT-allocable allocation on Line 9b after the OBBBA $40,400 cap took effect.[10, 1, 22]

Trusts and Estates Hit NIIT Almost Immediately — The $16,000 Threshold That Surprises Beneficiaries

For non-grantor trusts and estates, the NIIT threshold is dramatically lower than the individual threshold. Under §1411(a)(2), NIIT applies to undistributed net investment income above the dollar amount at which the highest §1(e) tax bracket begins for the year. Per IRS Revenue Procedure 2025-32 (the annual inflation-adjusted figures for 2026), that figure is $16,000 in 2026 — only 8 % of the $200,000 individual threshold and 6.4 % of the $250,000 joint threshold. The compressed §1(e) rate schedule that produces this number also subjects undistributed trust ordinary income above $16,000 to the top 37 % federal rate; combined with the 3.8 % NIIT, the marginal federal rate on undistributed trust ordinary investment income reaches 40.8 %, while qualified dividends and long-term capital gains face the same 23.8 % combined federal rate as for individuals.[4, 6, 27]

The single most powerful trustee strategy in NIIT planning is the distributable net income (DNI) distribution. When a non-grantor trust distributes NII to its beneficiaries during the tax year (or within 65 days of year-end under the §663(b) election), the income is "carried out" with its character intact: dividends remain dividends, interest remains interest, and crucially, the NIIT threshold test shifts from the trust's $16,000 to the beneficiary's individual threshold ($200,000 / $250,000). For a high-bracket trust holding $50,000 of NII, distributing all of it to a beneficiary whose MAGI is $150,000 produces zero combined NIIT — versus roughly $1,292 of NIIT (3.8 % × ($50,000 − $16,000)) if retained inside the trust. This DNI mechanic is governed by 26 CFR §1.1411-3 and Subchapter J of the Code, and trust accounting income (TAI) versus DNI character must be tracked separately for both federal income tax and NIIT.[6, 12, 4]

Several specialized trust types interact with NIIT in distinctive ways. Grantor trusts — including most revocable living trusts and intentionally defective grantor trusts (IDGTs) — are disregarded for income tax purposes, so all NII flows directly to the grantor's individual return and is tested against the $200,000 / $250,000 individual threshold. Charitable Remainder Trusts (CRTs) under §664 are themselves exempt from federal income tax (and thus from NIIT at the trust level), but distributions to non-charitable beneficiaries carry NII character through the §664 four-tier ordering rules — meaning beneficiaries effectively pay NIIT on the embedded investment-income components when distributions exceed cost basis. Electing Small Business Trusts (ESBTs) holding S-corporation stock have their own dedicated §1411 computation, with the S-corp portion taxed separately at the trust's top rate plus NIIT. Estate executors managing a decedent's final return and the post-death estate must coordinate Form 8960 with Form 1041 throughout the estate-administration period, often spanning several tax years.[21, 6, 12]

Real Estate, Passive Activity, and the §469(c)(7) Real-Estate-Professional Carve-Out

For most rental real estate, gross rental income is presumed passive under §469 regardless of how much time the owner spends managing the property. That presumption pulls rental income into NII Category 1, exposing the income (after deductions) to the 3.8 % NIIT once MAGI crosses the threshold. There is, however, a critical statutory exception: §469(c)(7) — the real-estate-professional rule. To qualify, a taxpayer must satisfy two annual tests: (1) more than 750 hours of personal services during the year in real property trades or businesses in which the taxpayer materially participates, and (2) more than 50 % of all of the taxpayer's personal services performed during the year are in real property trades or businesses. Both tests are evaluated jointly and must be substantiated with contemporaneous records.[20, 14, 7]

Qualifying as a real-estate professional under §469(c)(7) does not, by itself, exit rental income from NII. The taxpayer must also materially participate in each rental activity for which the income is to be treated as non-passive. Material participation is tested under one of the seven tests in 26 CFR §1.469-5T — most commonly the 500-hour test, the substantially-all test, or the 100-hour-with-no-greater-participant test. Many couples in real-estate-investing households elect under §1.469-9(g) to aggregate all rental real-estate activities as a single activity for material-participation testing, dramatically simplifying the hour-tracking burden across multiple properties. Once the taxpayer is both a §469(c)(7) real-estate professional and materially participating, the rental income shifts from passive Category 3 NII into a non-passive ordinary-trade-or-business category that the §1411(c)(1)(A)(i) carve-out excludes from NII entirely.[20, 7, 14]

The IRS scrutinizes real-estate-professional claims aggressively because the carve-out can shelter substantial annual rental income from both §469 passive-loss limitations and §1411 NIIT. Tax-court cases such as Bailey v. Commissioner, Hardy v. Commissioner, and Pourmirzaie v. Commissioner all turn on the adequacy of the taxpayer's contemporaneous time logs — court calendars, written notes, electronic timestamps, and detailed activity records. Generic estimates ("about 800 hours per year on real-estate matters") are routinely rejected. A separate but related exception exists for short-term rentals: when the average period of customer use is seven days or less (Reg §1.469-1T(e)(3)(ii)), the activity is not a "rental activity" within §469 at all, and material participation alone (without the §469(c)(7) qualification) suffices to make the income non-passive. This short-term-rental path is increasingly used by Airbnb and VRBO operators who do not otherwise qualify as full-time real-estate professionals.[20, 14, 7]

Eight Strategies to Reduce or Eliminate Your NIIT in 2026 — A Realistic Playbook

NIIT planning is fundamentally a problem of moving the needle on two variables — net investment income and MAGI — by reorganizing where, when, and through what vehicle investment income is recognized. The eight strategies below are ranked roughly by realism for the 2026 investor, with §-cited statutory hooks that anchor each move. None of them require aggressive interpretation of the Code; all are documented in IRS publications and used routinely by tax practitioners. Quantitative outcomes depend on each filer's specific MAGI, NII, state tax rate, and time horizon, so we use representative scenarios rather than universal claims.[1, 11]

Strategy 1 — Maximize tax-advantaged accounts. Every dollar of dividends, interest, or realized gain inside a 401(k), 403(b), 457(b), Traditional IRA, Roth IRA, or HSA is permanently outside NII under §1411(c)(5) and the §223 health-savings-account framework. Maximize 2026 contribution limits per IRS Rev. Proc. 2025-32 and Notice 2025-67. Strategy 2 — Asset location. Hold high-tax-cost assets (taxable bonds, REITs, high-turnover active funds) in tax-advantaged accounts; hold tax-efficient assets (broad-market index ETFs, municipal bonds, qualified-dividend payers) in taxable. Vanguard's tax-efficient-investing research has shown asset-location decisions can recover 0.20–0.45 percentage points per year in after-tax return for high-bracket investors — a meaningful chunk of which is NIIT-driven. Strategy 3 — Tax-loss harvesting. Realize losses in taxable accounts to offset Form 8960 Line 5 capital-gains amounts. Be mindful of the §1091 wash-sale rule, which (for now) does not apply to crypto but does apply to substantially identical equity securities.[27, 11, 1]

Strategy 4 — Municipal bonds. Tax-exempt interest under §103 is excluded from both NII and MAGI — a uniquely "double exclusion" lever. For a high-bracket investor in a high-tax state (e.g., California), the after-tax yield comparison can favor a 4 % muni over a 6 % corporate. Strategy 5 — Roth-account income. Qualified Roth distributions (post-five-year, post-59½) are tax-free and not NII. Long-run accumulation in Roth accounts produces retirement income that does not appear anywhere on Form 8960 — extraordinarily powerful for high-MAGI retirees. Strategy 6 — Installment sales. Under §453, the seller of a non-publicly-traded asset can spread realized gain over multiple tax years, keeping each year's MAGI below the threshold. Note the §453A interest charge for deferrals exceeding $5 million in any installment-method receivables, which can erode some of the benefit.[18, 11]

Strategy 7 — Charitable Remainder Trusts (CRTs). Under §664, a CRT is itself exempt from federal income tax, allowing highly appreciated assets to be sold inside the trust without immediate capital-gains recognition. The trust pays the donor a fixed annuity (CRAT) or unitrust percentage (CRUT) for life or a term of years, with the remainder passing to charity. The annuity payments carry NII character through the four-tier ordering rules, but the timing flexibility — combined with a partial charitable deduction at funding — can substantially reduce lifetime NIIT for donors with concentrated low-basis positions. Strategy 8 — Qualified Opportunity Zones (QOZs). Under §1400Z-2, eligible capital gains can be deferred and partially excluded by reinvesting in a QOZ Fund within 180 days. OBBBA Section 70421 modified and made permanent several QOZ provisions for investments after 2026; consult the most current IRS guidance because the OBBBA-modified QOZ regime differs materially from the original 2017 TCJA design.[21, 23, 11]

A practical caution applies to all eight strategies: the actual NIIT savings depend on each filer's margins. A household just barely over the $250,000 MFJ threshold benefits much less from MAGI reduction than a household at $400,000 of MAGI, because the lesser-of test means the second variable (MAGI − threshold) is the binding constraint near the threshold. Conversely, a retiree with $50,000 of NII and $300,000 of MAGI benefits more from NII-reduction strategies (munis, asset location) than from MAGI-reduction strategies, because NII is the binding variable. Modeling each strategy quantitatively for your specific MAGI–NII pair is essential before commitment, particularly for irreversible moves like CRT funding or QOZ deployment. Use the Sharpe ratio calculator to assess how NIIT-aware portfolio construction affects risk-adjusted returns over realistic time horizons.[1, 11, 10]

Roth Conversions and the NIIT MAGI Trap — Why Converting Triggers Higher NIIT on Other Income

A Roth conversion — moving pre-tax dollars from a Traditional IRA, 401(k), or 403(b) into a Roth IRA — produces a peculiar interaction with NIIT that catches even experienced advisors off guard. The conversion amount itself is not net investment income (it is a retirement-plan distribution excluded by §1411(c)(5)), but the conversion does increase MAGI on Form 1040 Line 11 because the converted amount is included in adjusted gross income. The result: in a year of large conversion, MAGI rises but the Form 8960 Line 12 NII figure does not — so the lesser-of test in Part III may now be binding on existing dividends, interest, and gains that were previously below the MAGI excess.[3, 13, 16]

A worked example clarifies the trap. Suppose a married couple filing jointly has $230,000 of wages, $20,000 of taxable dividends, and $10,000 of interest in a normal year — MAGI $260,000, NII $30,000, MAGI excess over the $250,000 threshold of $10,000. Their NIIT is 3.8 % × min($30,000, $10,000) = $380. Now they execute a $100,000 Roth conversion in the same year. Wages and NII unchanged at $260,000 of base earnings, but MAGI rises to $360,000. The MAGI excess jumps to $110,000, and NII remains $30,000 (the conversion is excluded under §1411(c)(5)). The new NIIT is 3.8 % × min($30,000, $110,000) = $1,140 — three times the original NIIT bill, despite no change in actual investment income. The marginal NIIT cost of the $100,000 conversion is $760 ($1,140 − $380), an effectively-2.5 % surtax on top of the conversion's ordinary-income tax.[3, 16]

Two planning responses follow naturally. First, multi-year conversion ladders that keep each year's MAGI just below the threshold (or at least below the level at which existing NII becomes the binding constraint) sharply reduce lifetime NIIT exposure. A retiree with $30,000 of NII and a $250,000 MFJ threshold can convert up to $20,000 per year (bringing MAGI to $250,000) without triggering any new NIIT on existing dividends and interest. Second, MFS-status filers face a particularly punitive trap because the $125,000 threshold is reached on far smaller conversions; couples whose financial circumstances suggest MFS filing should explicitly model conversion timing across multiple years before executing. Cross-link to our existing Roth IRA conversion guide for deeper coverage of the conversion mechanics; this section's focus is the §1411 interaction specifically.[1, 16]

State-Level Interactions: No State NIIT, but the OBBBA-Modified SALT Cap Reshapes Your Form 8960 Line 9b

NIIT is exclusively a federal-level tax. No U.S. state imposes its own NIIT-equivalent surtax on investment income; California, New York, and other high-tax states tax investment income only through their ordinary income-tax rate schedules, without a separate 3.8 % overlay. However, state ordinary income tax on the same investment income can substantially compound the federal-NIIT burden: a California resident in the top state bracket (13.3 %) realizing long-term capital gains pays a combined federal-NIIT-state rate of approximately 37.1 % (20 % federal LTCG + 3.8 % NIIT + 13.3 % state) on the realized portion. For ordinary investment income (e.g., taxable bond interest), the same resident faces 37 % federal + 3.8 % NIIT + 13.3 % state = roughly 54.1 % combined marginal — among the highest investment-income tax rates in the developed world.[28, 1, 10]

The interaction with the SALT cap is critical for high-income investors. §164(b)(6), as amended by OBBBA (Pub. L. 119-21, July 4, 2025), raised the federal SALT-deduction cap from the original $10,000 (TCJA) to $40,000 for tax year 2025, indexed at +1 % per year through 2029 — making the 2026 cap $40,400. The cap reverts to $10,000 for tax year 2030 unless extended by future legislation. The cap is subject to a high-MAGI phaseout: it begins to reduce by 30 cents for every $1 of MAGI above $505,000 in 2026 ($252,500 for MFS), with a minimum floor of $10,000 even at very high MAGI levels. This MAGI-phaseout structure means that a top-bracket investor whose MAGI substantially exceeds $505,000 receives only the pre-OBBBA $10,000 cap in practice.[22, 23, 28]

On Form 8960, this matters in Line 9b — the deduction for state, local, and foreign income tax allocable to NII. The amount that can be reported here is limited to the SALT-cap-allowable portion of the relevant state tax that is attributable to NII (typically computed as state tax × NII / total taxable income). For a high-MAGI investor whose total state tax exceeds the OBBBA cap, only the deductible portion (capped portion × NII fraction) flows through to Line 9b — meaning a substantial part of state tax on investment income provides no federal NIIT-deduction benefit. This is one reason municipal bonds (whose interest is excluded from both federal income tax and the state income tax in many states for in-state issuers) present particularly clean NIIT planning value: there is no state tax to allocate, no SALT-cap interaction, and no NIIT-deductibility puzzle. PTET (Pass-Through Entity Tax) workarounds in 36+ states also remain a viable avenue for high-income partnership and S-corp owners; the IRS Notice 2020-75 framework that authorized the workaround was preserved by OBBBA.[22, 23, 10, 28]

Frequently Asked Questions About the 3.8% Net Investment Income Tax

The questions below address the most common practitioner-and-investor questions about the Net Investment Income Tax in 2026. Each answer cites the underlying statutory or regulatory authority. Use this section as a quick reference when reviewing your own Form 8960 or interpreting NIIT communications from a tax advisor.