Margin interest gets reported on Line 9 of Schedule A (Form 1040), in the “Interest You Paid” section. Before it lands there, the amount usually has to pass through Form 4952, which decides how much of what you paid is actually deductible this year. So the short answer to where to report margin interest on a 1040 is: Form 4952 first, then Schedule A Line 9, then into your itemized deductions total on Form 1040.
The number you paid and the number you write off are often different. That’s the part worth understanding before you start filling in boxes.
The Form 4952 Step
Margin interest is “investment interest” under Section 163(d) of the Internal Revenue Code, meaning interest on money borrowed to buy property held for investment. Form 4952 is the worksheet the IRS uses to cap that deduction at your net investment income for the year.
You can skip Form 4952 and put the interest straight on Schedule A Line 9 only if all three of these are true:
- Your investment income from interest and ordinary dividends (minus any qualified dividends) is more than your total investment interest expense.
- You have no other deductible investment expenses to report.
- You have no disallowed investment interest carried over from a prior year.
If any one of those fails, the form is required and gets attached to your return.1Internal Revenue Service. Form 4952 – Investment Interest Expense Deduction The form is short. Filing it whenever you have margin interest is the safer default.
How Much You Can Actually Deduct
The rule is simple to state. You can deduct investment interest only up to your net investment income for that year. Pay $8,000 in margin interest with $5,000 of net investment income, and your deduction this year is $5,000.2Office of the Law Revision Counsel. 26 U.S. Code 163 – Interest
The other $3,000 isn’t gone. It carries forward and is treated as if you paid it next year, and it keeps rolling until your investment income absorbs it.2Office of the Law Revision Counsel. 26 U.S. Code 163 – Interest
What Counts as Net Investment Income
Net investment income is the ceiling, so the number matters. It’s the gross income from property held for investment, minus investment expenses other than interest.2Office of the Law Revision Counsel. 26 U.S. Code 163 – Interest Investment income includes taxable interest from bonds and bank accounts, ordinary dividends, annuities, royalties, and short-term capital gains. Passive activity income and rental income are excluded.
Qualified dividends and net long-term capital gains are left out by default, because they get lower tax rates. You can elect on Form 4952 to include some or all of them, which raises your ceiling but strips the elected amount of its preferential rate.1Internal Revenue Service. Form 4952 – Investment Interest Expense Deduction The election is nearly permanent, revocable only with IRS consent. Do the math first: the election helps only when the extra interest deduction saves more tax than the rate bump costs.
The “minus investment expenses” part of net investment income is effectively dead for most people. Those expenses used to be miscellaneous itemized deductions subject to the 2% AGI floor, a category the Tax Cuts and Jobs Act of 2017 suspended and that has since been made permanent.3Legal Information Institute. Tax Cuts and Jobs Act of 2017 (TCJA) For most individual filers, net investment income now just equals investment income.
Filling Out Form 4952
The form has three parts, and they follow the logic above.
Part I collects the interest itself. Line 1 is total investment interest paid during the year, which your broker reports on your year-end statement or consolidated 1099 as “margin interest” or “investment interest expense.” This is interest you paid, so it won’t show up on the 1099-INT among your interest income. Line 2 is any disallowed interest carried forward from last year’s Form 4952. Line 3 adds them.
Part II builds net investment income. Line 4a is gross investment income, including anything reported on a Schedule K-1 from a partnership or S corporation.4Internal Revenue Service. Form 4952 – Investment Interest Expense Deduction Lines 4b through 4f handle qualified dividends and net capital gains, and Line 4g is where any elected amount goes. Line 5 is other investment expenses, which for most filers is zero. Line 6 is the net.
Part III does the comparison. Line 7 shows any current-year disallowed expense that carries to next year. Line 8 is the smaller of Line 3 or Line 6, and that’s your deduction.1Internal Revenue Service. Form 4952 – Investment Interest Expense Deduction
Moving the Number to Schedule A
Take the figure from Line 8 of Form 4952 and enter it on Line 9 of Schedule A, under “Interest You Paid.”5Internal Revenue Service. 2025 Schedule A (Form 1040) It combines with your mortgage interest on Line 10, flows into your total itemized deductions at the bottom of Schedule A, and that grand total moves to Form 1040 as a subtraction from adjusted gross income.
All of this only helps if you itemize. For 2026, the standard deduction is $16,100 for single filers and $32,200 for married couples filing jointly.6Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 Margin interest by itself rarely gets you above that. Combined with mortgage interest and the $10,000 SALT cap, it often does.
Situations That Limit or Complicate the Deduction
Margin Used to Buy Tax-Exempt Securities
Interest on money borrowed to buy tax-exempt investments like municipal bonds is not deductible. The IRS doesn’t allow an interest deduction for debt used to produce tax-free income. If you hold munis and taxable securities in the same margin account, you have to allocate the debt and exclude the portion tied to tax-exempt holdings.
What You Actually Bought With the Borrowed Money
The IRS traces interest expense by following borrowed funds to what they paid for. Under Treasury Regulation 1.163-8T, interest is allocated based on the use of the proceeds; only interest on debt used for investment expenditures counts as investment interest under Section 163(d).7eCFR. 26 CFR 1.163-8T – Allocation of Interest Expense Among Expenditures Withdraw margin funds for personal spending and that share of the interest falls outside the deduction. Keep records of what the borrowed money bought.
Alternative Minimum Tax
If you’re subject to AMT, you may need to run a separate Form 4952 using AMT-adjusted figures, with the difference reported on Form 6251. For AMT purposes, you have to include interest that would have been deductible if tax-exempt interest on private activity bonds were treated as taxable income.8Internal Revenue Service. Instructions for Form 6251 (2025) Straightforward margin accounts don’t usually trigger this. Private activity bonds or large preference items are the reason to check.