Is Investment Interest Expense an Itemized Deduction?

Yes. Investment interest expense is an itemized deduction, claimed on Schedule A of Form 1040 after you calculate the allowable amount on Form 4952. The deduction covers interest you pay on money borrowed to buy or hold taxable investments — most commonly margin interest from a brokerage account — and it’s capped at your net investment income for the year, with any excess carrying forward indefinitely.¹ Because it lives on Schedule A, you only benefit if your total itemized deductions exceed the standard deduction for your filing status.

What Qualifies as Investment Interest Expense

Investment interest expense is interest you pay on debt used to buy or carry property held for investment. Margin interest is the classic example. What matters is the purpose of the loan, not what secured it: if you take out a personal loan and use the proceeds to buy stock, that interest qualifies.²

Several categories of interest are specifically excluded and belong elsewhere on your return, or nowhere at all:

Personal interest — credit cards, auto loans, and other consumer debt — is never deductible.
Home mortgage interest has its own itemized deduction with separate rules.
Interest on loans used to fund rental properties or businesses in which you don’t materially participate is passive activity interest, reported on Form 8582 rather than Form 4952.²
Interest on debt used to buy tax-exempt securities such as municipal bonds is disallowed entirely.³

If a single loan funded a mix of purposes, allocate the interest according to how you actually spent the proceeds. The IRS traces borrowed funds to specific expenditures, so clean records of how you deployed the money matter.²

The Net Investment Income Cap

Your deduction can’t exceed your net investment income for the year. Pay $15,000 in margin interest but earn only $10,000 in net investment income, and your current-year deduction is $10,000. The other $5,000 carries into next year.¹

Net investment income is your investment income minus your investment expenses. Investment income here means gross income from property held for investment: interest, ordinary (non-qualified) dividends, annuities, royalties, and investment income passed through from a partnership or S corporation on a Schedule K-1. Short-term capital gains from investment property are included; long-term capital gains and qualified dividends are excluded by default because the statute stops the calculation at net capital gain.¹ Passive activity income and expenses are never in this calculation — those rules run on a separate track.

Investment expenses that would otherwise reduce net investment income (advisory fees, custodial fees, research subscriptions) are no longer deductible for individuals. The Tax Cuts and Jobs Act suspended the miscellaneous itemized deduction for these costs, and the One Big Beautiful Bill Act made that suspension permanent.⁴ The practical effect: with no investment expenses to subtract, net investment income equals gross investment income, and the ceiling for your interest deduction is a little higher than it would have been before 2018.

The cap applies to individuals, estates, and trusts. Corporations aren’t subject to it.²

The Capital Gains Election

When investment interest expense outruns ordinary investment income, you can elect on Form 4952 to reclassify some or all of your long-term capital gains and qualified dividends as investment income. That lifts the ceiling and lets you deduct more interest now. The cost: any amount you reclassify loses its preferential rate and is taxed at your ordinary rate instead.²

Consider $30,000 in margin interest, $10,000 in ordinary investment income, and $20,000 in qualified dividends. Without the election, you deduct $10,000 and carry $20,000 forward. Elect to include the dividends, and you deduct the full $30,000 this year, but those dividends move from a 0%, 15%, or 20% rate to your marginal ordinary rate. Whether the trade pays off depends on the spread between those rates and how quickly you’d otherwise absorb the carryforward. Run both scenarios before you file, because once the election is on the return it can only be revoked with IRS consent.²

You Have to Itemize to Benefit

Because the deduction sits on Schedule A, it’s only useful if your total itemized deductions beat the standard deduction. For 2026, the standard deduction is $16,100 for single filers, $24,150 for heads of household, and $32,200 for married couples filing jointly.⁵

Add up your state and local taxes (capped at $40,000 for joint filers under current law), mortgage interest, charitable contributions, medical expenses above 7.5% of AGI, and your investment interest expense. If the total falls short of the standard deduction, itemizing costs you more than it saves, and the investment interest deduction stays on the shelf for the year.

The deduction reduces taxable income, not adjusted gross income. AGI is set before itemized deductions come off, so claiming investment interest doesn’t help you qualify for AGI-based tax breaks elsewhere on the return.⁶

How to Report It: Form 4952 and Schedule A

File Form 4952 if you’re claiming the deduction, if you’re subject to the net investment income limitation, or if you’re carrying forward disallowed interest from a prior year.² The form has three parts:

Part I totals your investment interest expense for the year, including any prior-year carryforward.
Part II calculates net investment income, incorporating the capital gains election if you make one.
Part III compares the two and produces your deductible amount.

The result from Part III flows to the “Interest You Paid” section of Schedule A.⁷

Carryforwards When the Cap Limits You

Excess investment interest expense isn’t lost. It’s treated as investment interest paid in the following tax year, and there’s no expiration on how long the balance can roll.¹ A $5,000 disallowed amount from 2025 becomes $5,000 of investment interest expense on your 2026 Form 4952, subject to that year’s net investment income limit.

The IRS doesn’t track the balance for you. If you lose your records, you lose the deduction. Keep every Form 4952 you file, because this year’s carryforward number is the starting point for next year’s calculation. The balance also survives years when you take the standard deduction — it doesn’t reset — but it can only be absorbed in a year when you itemize and have net investment income to run against.

Interaction with the 3.8% Surtax

A separate 3.8% net investment income tax applies when modified AGI exceeds $200,000 for single filers or $250,000 for joint filers. Those thresholds aren’t adjusted for inflation. The surtax uses its own definition of net investment income, but investment interest expense is allowed as a deduction against it. Claiming the deduction can reduce both regular income tax and the surtax, which is worth factoring in when you’re weighing the capital gains election.⁸

1
Office of the Law Revision Counsel. 26 U.S. Code 163 – Interest
2
Internal Revenue Service. Form 4952 – Investment Interest Expense Deduction
3
Office of the Law Revision Counsel. 26 U.S. Code 265 – Expenses and Interest Relating to Tax-Exempt Income
4
Thomson Reuters. What OBBB Means for Your Clients’ Itemized Deductions
5
Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
6
Internal Revenue Service. Topic No. 501, Should I Itemize?
7
Internal Revenue Service. About Form 4952, Investment Interest Expense Deduction
8
Office of the Law Revision Counsel. 26 U.S. Code 1411 – Imposition of Tax