Investment Interest Expense Deduction Calculator (Form 4952) 2026
Calculate the investment interest deduction limited to net investment income. Margin loan interest, Form 4952, ordinary-income election analysis, and indefinite carryforward tracker.
$
Margin loan interest, investment loan interest $
From prior year Form 4952 $
Taxable interest, ordinary dividends, STCG, royalties $
1099-DIV Box 1b β eligible for 0/15/20% rate $
LTCG eligible for 0/15/20% rate $0
Deductible Interest (Form 4952)
$0
Net Investment Income
$0
Carryforward to Next Year
$0
Tax Savings from Deduction
Form 4952 β Investment Interest Expense Calculation
Investment Interest Expense β Form 4952 Guide
Investment interest expense is the interest on loans used to purchase or carry investment property. The most common source is margin loan interest from a brokerage account. It is deductible as an itemized deduction on Schedule A, but only up to your net investment income (NII) for the year. Any excess carries forward indefinitely.
Form 4952 β Step by Step
Line 1: Investment interest paid this year
Line 2: Disallowed investment interest carried from prior year
Line 3: Total investment interest = Line 1 + Line 2
Line 4: Net investment income (ordinary + any elected cap gain amounts)
Line 5: Deductible investment interest = lesser of Line 3 or Line 4
Line 7: Carryforward = Line 3 β Line 5 (carries forward indefinitely)
Line 2: Disallowed investment interest carried from prior year
Line 3: Total investment interest = Line 1 + Line 2
Line 4: Net investment income (ordinary + any elected cap gain amounts)
Line 5: Deductible investment interest = lesser of Line 3 or Line 4
Line 7: Carryforward = Line 3 β Line 5 (carries forward indefinitely)
Example β $15,000 Margin Interest, $8,000 NII
Investment interest paid: $15,000
Net investment income (no election): $8,000 (ordinary only)
Deductible this year: $8,000
Carryforward: $7,000
At 24% bracket: tax savings = $8,000 Γ 24% = $1,920 this year
+ $7,000 carryforward deductible in future years against future NII.
Net investment income (no election): $8,000 (ordinary only)
Deductible this year: $8,000
Carryforward: $7,000
At 24% bracket: tax savings = $8,000 Γ 24% = $1,920 this year
+ $7,000 carryforward deductible in future years against future NII.
Extended
Ordinary-Income Election Analysis + Multi-Year Carryforward
When making the ordinary income election on qualified dividends and LTCG maximizes your total after-tax benefit
Ordinary Income Election β Should You Make It?
| Scenario | Deductible Interest | Tax Saved on Interest | Cap Gains Rate Cost | Net Benefit |
|---|
Carryforward Projection β Years Until Fully Used
Assumes same NII each year, no new investment interest, carryforward from this year applied.
| Year | Carryforward Start | Available NII | Deducted | Remaining Carryforward |
|---|
Key rule: Investment interest is only deductible if you itemize on Schedule A. If your total itemized deductions (mortgage interest + state taxes + charitable + investment interest) do not exceed your standard deduction ($15,000 single / $30,000 MFJ in 2026), the deduction provides no benefit and the interest still carries forward for future years when itemizing may be beneficial.
Frequently Asked Questions
What is investment interest expense and where is it deducted?
Investment interest expense is interest paid on money borrowed to buy or carry investment property β most commonly margin loan interest from a brokerage account. It is deductible on Schedule A (Form 4952) as an itemized deduction, limited to your net investment income (NII) for the year. NII includes ordinary dividends, taxable interest income, short-term capital gains, royalties, and annuity income β but does NOT include qualified dividends or long-term capital gains (unless you elect to treat them as ordinary income). Any investment interest that exceeds NII carries forward indefinitely to future years.
What is Net Investment Income and how is it calculated for Form 4952?
Net Investment Income (NII) for Form 4952 purposes = gross investment income minus investment expenses (other than investment interest). Gross investment income includes: taxable interest, ordinary dividends, short-term capital gains, royalties, annuity income, and passive income not from a passive activity. It does NOT include qualified dividends, long-term capital gains, or income from passive activities (which have their own rules). Post-TCJA, most investment expenses (advisory fees, etc.) are no longer deductible, so NII is typically just the income items.
Should I elect to treat qualified dividends and long-term capital gains as ordinary income for Form 4952?
You can elect to include some or all of your qualified dividends and net long-term capital gains in NII for Form 4952 purposes. This increases your NII ceiling, allowing more investment interest to be deducted in the current year. However, any amounts included in NII for this purpose lose their preferential 0/15/20% capital gains rate and are taxed at your ordinary income rate. This election is worth making only when the tax benefit from deducting more investment interest (at your marginal rate) exceeds the cost of losing the preferential capital gains rate on the reclassified dividends/gains. Run the math: it often helps investors in higher brackets with large margin loan balances.
Does investment interest expense apply to margin loans used to buy stocks?
Yes. Interest paid on a margin loan used to purchase or carry stocks or other investment securities is classified as investment interest expense and is deductible on Form 4952, limited to net investment income. Key requirements: (1) the loan must be used to buy taxable investments β not tax-exempt bonds, not your personal residence; (2) you must itemize deductions on Schedule A; (3) you must file Form 4952 to compute the deductible amount. If you use margin to buy municipal bonds, the interest is NOT deductible (disallowed under IRC 265 because the income is tax-exempt).
How long can investment interest expense carryforward?
Investment interest expense that exceeds net investment income in the current year carries forward indefinitely β there is no limit on the number of years it can carry. Each year, you apply the carryforward interest against that year's NII (plus the current-year interest) and any remaining excess continues to carry forward. This is particularly valuable for investors who had large margin loan interest in low-income years β the deduction eventually gets used when NII rises. You must file Form 4952 each year even if you have only a carryforward and no current-year investment interest.