US Investment Taxation: After-Tax Analysis Framework

Reference: Tax Years 2024 / 2025 | Sources: IRS publications, IRC code, Tax Foundation, IRS Rev. Proc. 2024-40

Part 1 — Federal Tax Rates on Investment Income

1.1 Ordinary Income Brackets (2025)

Rate	Single	Married Filing Jointly
10%	$0 – $11,925	$0 – $23,850
12%	$11,926 – $48,475	$23,851 – $96,950
22%	$48,476 – $103,350	$96,951 – $206,700
24%	$103,351 – $197,300	$206,701 – $394,600
32%	$197,301 – $250,525	$394,601 – $501,050
35%	$250,526 – $626,350	$501,051 – $751,600
37%	$626,351+	$751,601+

Standard deduction 2025: $15,000 single / $30,000 MFJ

Short-term capital gains, ordinary dividends, interest income, and IRA/401(k) withdrawals all use this schedule.

1.2 Long-Term Capital Gains (LTCG) Rates (2025)

Requires holding period > 1 year (IRC §1222).

Rate	Single	Married Filing Jointly
0%	$0 – $48,350	$0 – $96,700
15%	$48,351 – $533,400	$96,701 – $600,050
20%	$533,401+	$600,051+

Special rates: Collectibles max 28% (§1(h)(4)); Unrecaptured §1250 gain (real estate depreciation) max 25% (§1(h)(6)); QSBS max 28% on non-excluded portion.

1.3 Qualified vs. Ordinary Dividends

Ordinary dividends → ordinary income rates (10%–37%)

Qualified dividends (IRC §1(h)(11)) → LTCG rates (0%/15%/20%) if:

Paid by a US or qualified foreign corporation
Stock held >60 days in the 121-day window around the ex-dividend date
Not from money market funds, tax-exempt organizations

REIT ordinary dividends: Taxed as ordinary income (not qualified) but may qualify for the 20% QBI deduction under §199A, reducing effective max rate to 29.6% (37% × 80%).

1.4 Net Investment Income Tax (NIIT) — IRC §1411

A 3.8% surtax on the lesser of: net investment income (NII) OR Modified AGI above threshold.

Filing Status	MAGI Threshold
Single / HoH	$200,000
Married Filing Jointly	$250,000
MFS	$125,000

Critical: These thresholds are NOT inflation-indexed (frozen since 2013). More investors cross them every year with no legislative action required.

What is NII: Interest, dividends, annuities, royalties, rents, net investment property gains, passive activity income.

What is NOT NII: Wages, SS benefits, IRA/401(k) distributions, muni bond interest, §121 home sale exclusion, active business income.

Muni bond trap: Muni interest is excluded from NII but IS included in MAGI — it can push other investment income above the NIIT threshold, triggering 3.8% on that income.

Combined top federal rates:

LTCG + NIIT: 20% + 3.8% = 23.8%
Ordinary income + NIIT: 37% + 3.8% = 40.8%

Forms: Form 8960, IRS Publication 550

1.5 Alternative Minimum Tax (AMT) — IRC §§55–59

2025 exemptions:

Status	Exemption	Phase-Out Begins
Single	$88,100	$626,350
MFJ	$137,000	$1,252,700
MFS	$68,500	$626,350

AMT rates: 26% up to $239,100 AMTI (MFJ); 28% above.

How AMT affects investors:

ISO stock options: The spread on exercise is an AMT preference item — the biggest individual trigger
Private activity bond (PAB) interest: Tax-exempt for regular tax; AMT preference item → effective yield collapses at 26% AMT rate (e.g., 3.5% muni → 2.59% after-AMT)
LTCG rates are the same under AMT — no extra penalty on capital gains
TCJA significantly narrowed AMT through 2025 — primary exposure is ISO exercises and very high-income phase-out zone

Form: Form 6251

Part 2 — Investment Interest Expense Deduction (IRC §163(d))

This is the central provision for leveraged investing analysis.

2.1 What Qualifies

Interest paid on debt incurred to purchase or carry property held for investment. The debt must be traceable to investment property via the interest tracing rules (Temp. Reg. §1.163-8T).

Qualifying:

Margin loan interest to buy stocks/bonds
SBLOC interest when proceeds used to buy investments
Interest on credit lines traced to investment purchases

Does NOT qualify (wrong IRC section):

Situation	Governing Section
Passive activity interest	IRC §469
Qualified residence interest	IRC §163(h)
Interest traceable to tax-exempt income	IRC §265(a)(2) — fully disallowed
Business interest (active trade)	IRC §163(j)
Personal consumption debt	Non-deductible

2.2 The Core Limit

Investment interest expense is deductible only up to net investment income (NII):

NII = Gross Investment Income − Investment Expenses

Important: By default, LTCG and qualified dividends are excluded from NII — they use preferential rates and don’t count toward the §163(d) ceiling.

Additional restriction: The §163(d) deduction is an itemized deduction on Schedule A. If you take the standard deduction, you cannot claim it. With 2025 standard deductions at $15,000/$30,000, most middle-income taxpayers don’t itemize, making this deduction unavailable.

2.3 The Capital Gains Election (IRC §163(d)(4)(B))

You may elect to include all or part of your LTCG and/or qualified dividends in NII to allow more investment interest to be deducted.

The inescapable trade-off: Any amount elected into NII is taxed at ordinary income rates — you permanently lose preferential LTCG/qualified dividend treatment on that amount.

When the election makes sense:

You’re in a low ordinary income bracket where LTCG rate is already 0% (12% bracket or below — no cost to giving up preferential treatment)
You have large investment interest carryforwards and expect NII to shrink
Time value of current deduction outweighs the rate differential

How to elect: Form 4952, by the return due date (including extensions).

2.4 Carryforward

Disallowed investment interest carries forward indefinitely (IRC §163(d)(2)) — no expiration.

Part 3 — Leveraged Investing: Borrowing to Invest

3.1 Margin Account Interest

Classic §163(d) investment interest expense. Deductible up to NII via Form 4952 on Schedule A. Requires itemizing.

Rules:

Excess carries forward indefinitely
Must be traced to investment property purchases
Prepaid interest: deductible when accrued, not when paid (IRC §461 economic performance)
Interest on short positions: deductible if held for investment

3.2 Securities-Backed Lines of Credit (SBLOCs)

Portfolio is pledged as collateral; proceeds borrowed against it.

The loan itself is NOT taxable income — this is the foundation of “buy, borrow, die.”

Interest deductibility depends entirely on USE OF PROCEEDS, not the collateral:

Use of Proceeds	Deductibility
Buy investments	Investment interest under §163(d) — deductible up to NII
Personal consumption (car, vacation, living expenses)	Not deductible
Business operations	Business interest under §163(j)

Risks: Margin calls if collateral value drops → forced asset sales → unexpected taxable events.

3.3 Home Equity Loans / HELOCs Used for Investing

Pre-2018: Home equity interest was deductible up to $100,000 of debt regardless of use.

Post-TCJA (2018–2025) per IRS Publication 936: Home equity/HELOC interest is only deductible as home mortgage interest if proceeds are used to “buy, build, or substantially improve” the home securing the loan.

If you borrow via HELOC and invest the proceeds:

NOT deductible as home mortgage interest under §163(h)
May be reclassifiable as investment interest under §163(d) using the interest tracing rules (Temp. Reg. §1.163-8T) — deductible up to NII

TCJA expiration: TCJA provisions expire December 31, 2025. Without legislative extension, home equity interest for any use would again be deductible up to $100,000 — verify current law for 2026+.

Acquisition debt cap (post-December 15, 2017 loans): $750,000 deductible limit ($375,000 MFS). Pre-2018 loans grandfathered at $1,000,000 cap.

3.4 Business Loans Used for Investing

If borrowing occurs at the entity level (S-Corp, partnership, LLC with business operations):

Interest may be deductible as business interest under IRC §163(j)
Subject to 30% of adjusted taxable income limitation
Small businesses with ≤ $30M average annual gross receipts (2024) are exempt from §163(j)
Business interest limitation carryforwards are indefinite
This can be more favorable than the §163(d) NII ceiling for high-leverage situations

3.5 “Buy, Borrow, Die” — Tax Analysis

Phase	Tax Treatment
Buy appreciating assets	Unrealized appreciation: zero tax during life
Borrow against portfolio	Loan proceeds: not income (IRC §61/§1001)
Die	Heirs get stepped-up basis to FMV at death (IRC §1014) — lifetime appreciation permanently excluded from capital gains tax
Estate tax	Applies to net value; unified credit shields $13.99M (2025) per person; $27.98M per couple with portability

The interest deduction issue in “borrow to live” mode: If proceeds fund personal consumption, interest is not deductible anywhere. The strategy’s tax benefit comes from avoiding realization, not from interest deductions.

Estate tax exemption sunset risk: TCJA elevated exemption expires after December 31, 2025, reverting to ~$7M (inflation-adjusted) absent legislation. Major planning risk.

Policy risk: Academic and administration proposals have targeted this strategy (mark-to-market at death, billionaire minimum tax). Not enacted as of early 2026.

Part 4 — Wash Sale Rules (IRC §1091)

If you sell a security at a loss and buy a “substantially identical” security within 30 days before or after the sale (61-day window total), the loss is disallowed currently.

Effect: The disallowed loss is added to the cost basis of the replacement; the holding period carries over. The loss is deferred, not permanently lost — unless you trigger wash sales continuously, or do it across an IRA (see below).

IRA wash sale trap: If you sell at a loss in a taxable account and buy the same security in an IRA within 30 days, the loss is permanently lost (the basis in the IRA does not increase to compensate).

Crypto exception: Cryptocurrencies are not “securities” — wash sale rules don’t apply to Bitcoin, Ethereum, etc. as of early 2026. You can sell at a loss and immediately repurchase. Legislation to close this has been proposed but not enacted.

Leveraged investing interaction: When tax-loss harvesting leveraged positions, you must either wait 31 days (unhedged) or replace with a non-substantially-identical security. The “substantially identical” standard for similar index ETFs (e.g., SPY → IVV) is not definitively settled.

Part 5 — Passive Activity Rules (IRC §469)

5.1 Core Rule

Passive losses can only offset passive income. They cannot offset wages, active business income, or portfolio income (dividends, interest, capital gains). Excess passive losses carry forward.

Two categories of passive activity:

Business activities where you do NOT materially participate
All rental activities (with exceptions)

Portfolio income is explicitly excluded from passive income — you cannot use passive losses to shelter dividends or capital gains.

5.2 Material Participation — Seven Tests

You meet material participation if ANY one is satisfied:

Test	Requirement
1	>500 hours in the activity
2	Your participation is substantially all participation by anyone
3	>100 hours AND at least as much as anyone else
4	Multiple activities: each 100–500 hours, total >500 across all
5	Materially participated in 5 of prior 10 years
6	Materially participated in any 3 prior years (personal service businesses)
7	Regular, continuous, substantial (≥100 hours minimum)

5.3 The $25,000 Rental Loss Allowance

For rental real estate with active participation (meaningful management decisions — lower bar than material participation):

Up to $25,000 of rental loss offsets non-passive income
Phase-out: $1 lost per $2 of MAGI over $100,000
Eliminated entirely at $150,000 MAGI (MFJ)
Minimum 10% ownership required

Neither threshold is inflation-indexed — frozen since 1986.

5.4 Real Estate Professional Exception (IRC §469(c)(7))

Rentals become non-passive if — annually, both tests met:

>750 hours in real property trades/businesses in which you materially participate
>50% of all personal service time in real property businesses

If you qualify and materially participate in each rental, all rental losses are fully deductible against any income. The grouping election (Reg. §1.469-9(g)) lets you aggregate all rentals into one activity, making material participation much easier to satisfy.

5.5 At-Risk Rules Interaction (IRC §465)

At-risk rules apply before passive activity rules. Deductions are limited to your at-risk amount (cash + recourse debt + qualified non-recourse financing on real property). Standard commercial mortgages on real estate count as qualified non-recourse — they don’t limit deductions beyond equity. Seller financing or related-party loans may not count.

Part 6 — State Tax Variation

6.1 States with No Income Tax

State	Status
Texas, Florida, Nevada, Wyoming, South Dakota, Alaska	No income tax; no capital gains tax
Washington	7% capital gains excise tax on LTCG >$262,000 (individual) from 2023; real estate gains exempt; no income tax
Tennessee	No income tax (investment income tax repealed 2023)
New Hampshire	No wages tax; interest/dividends taxed at 3% (2024), eliminated after 2025

Washington is the critical outlier — the only “no income tax” state with a capital gains tax, enacted 2023, upheld by WA Supreme Court.

6.2 Capital Gains Rates — High-Tax States

Most states with income taxes treat capital gains as ordinary income — no preferential rate.

State	Effective Cap Gains Rate	Notes
California	Up to 13.3%	Highest in US; no preferential LTCG treatment
New York (NYC)	State up to 10.9% + NYC up to 3.876% = ~14.8%	NYC residents face highest combined rates in world
Oregon	Up to 9.9%	Ordinary income treatment
Minnesota	Up to 9.85%	Ordinary income treatment
New Jersey	Up to 10.75%	Ordinary income treatment
Illinois	4.95% flat	Flat rate on all income
Massachusetts	5% most income; 8.5% short-term (<1 year)	One of few states with separate short-term rate

Combined top rates on LTCG (2025):

Investor Location	Federal LTCG	NIIT	State	Combined
Texas / Florida	20%	3.8%	0%	23.8%
Illinois	20%	3.8%	4.95%	28.75%
New York State	20%	3.8%	10.9%	34.7%
New York City	20%	3.8%	10.9% + 3.876%	38.6%
California	20%	3.8%	13.3%	37.1%

6.3 Investment Interest Deduction — State Conformity

Most states use federal AGI as their starting point → §163(d) limitation generally flows through automatically.

Notable exceptions:

California: Conforms to §163(d) but does NOT conform to the TCJA suspension of miscellaneous itemized deductions — investment expenses (advisory fees, etc.) may still be deductible in California, increasing the NII ceiling and thus the §163(d) deduction
New York: Generally conforms to federal §163(d) rules
States that compute income independently (not from federal AGI) — verify state-specific rules

Part 7 — Municipal Bond Interest

7.1 Federal Exemption

Interest on state/local government bonds is excluded from gross income under IRC §103. This is a statutory exclusion, not a deduction.

Excluded: General obligation bonds, revenue bonds for governmental purposes, qualifying private activity bonds (if not AMT preference items).

NOT excluded: Capital gains from selling munis (LTCG rates apply); market discount on bonds purchased below adjusted issue price (ordinary income when realized).

7.2 AMT and Private Activity Bonds (PABs)

Bonds where >10% of proceeds benefit private business use (airports, hospitals, student loans, low-income housing):

Regular tax: exempt
AMT: preference item under IRC §57(a)(5) — added back into AMTI

After-AMT yield example: 3.5% PAB yield, investor at 26% AMT → effective yield = 3.5% × (1 − 0.26) = 2.59%

Mutual funds and ETFs disclose the percentage of income subject to AMT in prospectuses.

7.3 State Tax Treatment

Own-state bonds: Generally exempt from state income tax in the issuing state
Out-of-state bonds: Most states tax interest on other states’ bonds
US territory bonds (Puerto Rico, Guam, USVI): Triple-exempt — federal, state, and local tax exempt in all states — a meaningful planning tool
Some states (Illinois, Iowa, Wisconsin — verify annually) exempt all muni interest regardless of source

7.4 Tax-Equivalent Yield

Tax-Equivalent Yield = Muni Yield ÷ (1 − Combined Marginal Rate)

For combined federal + state + NIIT analysis:

Example — California resident, top brackets:

Federal ordinary + NIIT: 37% + 3.8% = 40.8%
California state: 13.3%
Combined: 54.1%
A 3.0% muni bond → tax-equivalent yield: 3.0% ÷ (1 − 0.541) = 6.54%

NIIT interaction caveat: Muni interest is excluded from NII but included in MAGI — it can push other NII above the $200K/$250K NIIT threshold, making the effective tax cost higher than this formula shows.

Social Security interaction: Muni interest is included in the “provisional income” formula for Social Security taxability (IRC §86). A hidden cost for retirees near the SS thresholds.

Part 8 — Retirement Accounts

8.1 Core Tax Character Issue

Inside traditional IRA/401(k): All gains — whether capital gains, qualified dividends, or interest — eventually come out as ordinary income. There are no preferential LTCG rates. This makes traditional accounts suboptimal for assets that would otherwise generate LTCG.

Inside Roth IRA/401(k): All qualified distributions are tax-free. All tax character is erased in the best possible way — particularly valuable for high-appreciation assets and ordinary-income-generating investments (bonds, REITs, high-turnover strategies).

8.2 UBTI — Unrelated Business Taxable Income in IRAs (IRC §§511–514)

IRAs are subject to Unrelated Business Income Tax (UBIT) when they earn UBTI.

What triggers UBTI in an IRA:

Active business income: IRA owns an operating business via LLC or directly.
Leveraged real estate — UDFI (Unrelated Debt-Financed Income, IRC §514): When an IRA borrows money (e.g., non-recourse mortgage on rental property), the income attributable to the financed portion is UBTI.
- Example: IRA with a 40% non-recourse mortgage → 40% of gross rental income = UBTI
- UBTI is taxed at trust/estate rates, which hit 37% at only $15,650 of income (2025)
MLPs in IRAs: MLPs typically generate UBTI from their operating business — a well-known pitfall. The K-1 income that is tax-efficient in a taxable account becomes UBTI inside an IRA.

What does NOT trigger UBTI: Portfolio income (dividends, interest, capital gains from selling securities) — explicitly excluded by IRC §512(b).

Leveraged ETFs in IRAs: Generally do NOT create UBTI. The leverage is internal to the ETF wrapper (derivatives/swaps/futures) — the IRA simply owns shares. UBTI risk only arises if the IRA itself borrows money.

Threshold: UBTI must exceed $1,000 gross before UBIT applies. Form 990-T.

Part 9 — Complete Threshold Reference (2024/2025)

Item	2024	2025	Indexed?
Top bracket (37%) — Single	$609,351	$626,351	Yes
Top bracket (37%) — MFJ	$731,201	$751,601	Yes
LTCG 0% — Single	≤ $47,025	≤ $48,350	Yes
LTCG 0% — MFJ	≤ $94,050	≤ $96,700	Yes
LTCG 20% — Single	> $518,900	> $533,400	Yes
LTCG 20% — MFJ	> $583,750	> $600,050	Yes
NIIT threshold — Single	$200,000	$200,000	No
NIIT threshold — MFJ	$250,000	$250,000	No
AMT exemption — Single	$85,700	$88,100	Yes
AMT exemption — MFJ	$133,300	$137,000	Yes
Estate tax exemption (per person)	$13,610,000	$13,990,000	Yes
Rental loss allowance phase-out begins	$100,000 MAGI	$100,000 MAGI	No
Rental loss allowance eliminated	$150,000 MAGI	$150,000 MAGI	No
Standard deduction — Single	$14,600	$15,000	Yes
Standard deduction — MFJ	$29,200	$30,000	Yes
QBI phase-out begins — MFJ	$364,200	$394,600	Yes
QBI phase-out ends — MFJ	$464,200	$494,600	Yes
401(k) contribution limit	$23,000 ($30,500 age ≥50)	$23,500 ($31,000 age ≥50)	Yes
IRA contribution limit	$7,000 ($8,000 age ≥50)	$7,000 ($8,000 age ≥50)	Yes

Part 10 — Key IRC Sections and IRS Forms

Topic	IRC Section	Form / Publication
Capital gains	§§1221–1256	Schedule D, Pub. 550
NIIT	§1411	Form 8960, Topic 559
Investment interest	§163(d)	Form 4952, Pub. 550
Home mortgage interest	§163(h)	Publication 936
Business interest limitation	§163(j)	Form 8990
Passive activity rules	§469	Form 8582, Pub. 925
At-risk rules	§465	Form 6198
AMT	§§55–59	Form 6251, Topic 556
Muni bond exemption	§103	Pub. 550
PABs / AMT preference	§§141, 57(a)(5)	Pub. 550
Wash sale rules	§1091	Pub. 550
QBI deduction	§199A	Form 8995/8995-A
UBTI in IRAs	§§511–514	Form 990-T, Pub. 598
Step-up in basis	§1014	Pub. 559
Estate tax	§§2001–2058	Form 706

Summary: 10 Rules for After-Tax Investment Analysis

Top federal rate on ordinary investment income is 40.8% (37% + 3.8% NIIT). On LTCG: 23.8% (20% + 3.8%). State adds further.
NIIT thresholds are frozen at 2013 levels ($200K/$250K). As inflation raises incomes, more investors are caught each year without any legislative action.
§163(d) investment interest deduction is limited to net investment income AND requires itemizing. Most investors below top brackets take the standard deduction and cannot access this deduction at all.
Loan proceeds are not taxable income. Deductibility of the interest depends entirely on use of proceeds, not what secures the loan.
HELOC interest used for investing is not deductible as mortgage interest post-TCJA (2018–2025). It may be reclassifiable as investment interest under tracing rules — but then subject to the NII ceiling.
The LTCG election to expand §163(d) always costs you at ordinary rates — it only makes mathematical sense when your ordinary rate is at or below your LTCG rate.
Passive losses cannot offset wages or portfolio income — only other passive income. The $25,000 rental allowance phases out entirely at $150,000 MAGI (both thresholds non-indexed since 1986).
UBTI applies when an IRA borrows (UDFI) — leveraged ETFs in IRAs typically do not trigger this because leverage is inside the fund wrapper, not at the IRA level.
Washington State’s 7% capital gains tax is a critical outlier among “no income tax” states. No other state in that category has enacted a capital gains levy.
TCJA expires December 31, 2025. Individual brackets, standard deductions, AMT exemptions, QBI deduction, home equity interest rules, and the ~$14M estate tax exemption are all affected. Verify current law for 2026 planning.

This framework reflects law as of early 2026. Tax law changes frequently. For specific situations, verify against current IRS publications or consult a qualified tax professional.