Is Securities-Based Line of Credit Interest Tax Deductible?

Interest paid on a securities-based line of credit is tax deductible only when the borrowed money is spent on something the tax code treats as deductible, such as an investment property or an active business. The collateral does not matter. What matters is where the cash went, because the IRS classifies interest by the use of the proceeds, and each classification has its own rules and limits.

What Actually Decides Whether the Interest Is Deductible

The IRS applies “tracing rules” to interest expense. Money borrowed on an SBLOC is followed from the lender to whatever you ultimately buy or pay for, and that final use assigns the interest to a category.¹ Pledging your brokerage account as collateral does nothing on its own. A dollar spent on a vacation produces non-deductible personal interest whether it came from a credit card, a personal loan, or an SBLOC drawn against a seven-figure portfolio.

One thing an SBLOC cannot fund, by the terms of the loan itself: buying more securities. SBLOCs are “non-purpose” loans under Federal Reserve Regulation U, meaning the proceeds cannot be used to purchase or carry margin stock.² The realistic deductible uses are investment real estate, capital for a business you actively run, and other non-securities investments.

The Three Categories That Matter

Section 163 of the Internal Revenue Code sorts interest into categories with very different outcomes:

Investment interest, for debt used to acquire or carry property held for investment (rental land, precious metals, other non-securities investment assets). Deductible up to your net investment income for the year.³
Business interest, for debt used in a trade or business in which you materially participate. Deductible subject to a separate cap tied to business income.³
Personal interest, for anything that is not investment, business, passive activity, or qualified residence related. Not deductible at all.³

Two edge cases sit alongside these. Proceeds used for a rental property or a business in which you do not materially participate produce passive activity interest, deductible only against passive income.⁴ Proceeds used to buy, build, or substantially improve your primary or secondary home may qualify as deductible residence interest, subject to the $750,000 acquisition debt limit ($375,000 if married filing separately).⁵

Investment Interest: The Net Investment Income Cap

When SBLOC interest qualifies as investment interest, you can deduct it only up to your net investment income (NII) for the year. NII is investment income minus investment expenses, excluding the interest itself.³

Investment income for this calculation generally includes taxable interest, non-qualified dividends, royalties, and short-term capital gains. Qualified dividends and long-term capital gains are excluded by default because they already receive preferential tax rates. On the expense side, the permanent elimination of miscellaneous itemized deductions means advisory and custodial fees no longer reduce NII for most taxpayers.⁶

The Qualified Dividend and Long-Term Gain Election

If your investment interest exceeds NII, you can elect on Form 4952, line 4g to pull some or all of your qualified dividends and long-term capital gains into NII. Every dollar you reclassify loses its preferential rate (0%, 15%, or 20%) and gets taxed at ordinary income rates instead.¹ For someone in the 37% bracket with heavy SBLOC interest and thin ordinary investment income, the math can work. For most borrowers, it deserves a careful calculation, not a reflex.

Carryforward of the Excess

Investment interest disallowed by the NII cap is not lost. It carries forward indefinitely and is added to next year’s investment interest, still subject to the NII cap each year.⁷ Pay $40,000 in SBLOC interest on a rental land purchase against $30,000 of NII, and you deduct $30,000 now and carry $10,000 into next year.

Business Interest and the 163(j) Cap

SBLOC proceeds injected into a business you materially participate in produce business interest. The deduction is capped at business interest income plus 30% of adjusted taxable income (ATI) from that business.³ Since 2022, ATI is calculated on an EBIT basis, so depreciation and amortization are no longer added back. That tightens the cap for capital-intensive businesses.

Small businesses escape the cap entirely if average annual gross receipts over the prior three years fall below the inflation-adjusted threshold, which is $32 million for 2026. Meet that test and the full amount of business interest from the SBLOC is deductible.

Uses That Produce No Deduction

Personal spending is the biggest zero. Tuition, vacations, a personal car, general living expenses: interest on SBLOC dollars spent this way is personal interest and produces no tax benefit.³

A less obvious trap: buying tax-exempt securities. If you use SBLOC proceeds to purchase municipal bonds or other federally tax-exempt obligations, interest on the debt allocable to those holdings is non-deductible. The IRS does not let you deduct borrowing costs used to generate tax-free income.⁸

A narrower one: if SBLOC proceeds fund positions that are part of a straddle, the interest and carrying charges must be capitalized into the cost of the position rather than deducted in the current year.⁹

Tracing in Practice

The 30-Day Window

You do not need to spend SBLOC money the moment it arrives. Any expenditure made from any of your accounts, or from cash, within 30 days before or 30 days after the SBLOC deposit is treated as made from those proceeds.¹ So you can close on the investment property first and draw a few weeks later, or draw first and close within a month, without breaking the tracing chain.

Mixed-Use Draws

Split a $100,000 draw into $80,000 for an investment property and $20,000 for personal expenses, and 80% of the interest is investment interest while 20% is non-deductible.¹

When you repay a mixed-use balance, the IRS actually helps you: repayments are applied against the personal-use portion first, so the non-deductible share shrinks and the deductible percentage of the remaining balance improves over time.¹

Keep the Money Separate

Commingling SBLOC proceeds with other funds makes tracing hard to prove in an audit. The cleanest approach is to deposit SBLOC draws into a dedicated account and pay directly from it. Keep loan statements showing interest paid and balances, bank or brokerage records showing the deposit and its disbursements, and purchase documentation tying each disbursement to a specific asset.¹⁰

The NIIT Side Benefit

Investment interest that clears the NII cap also reduces the 3.8% Net Investment Income Tax base. The NIIT applies to modified adjusted gross income above $200,000 (single), $250,000 (married filing jointly), or $125,000 (married filing separately). Those thresholds are not indexed for inflation.

The deduction flows onto Form 8960, line 9a, but only the amount actually allowed under the regular NII cap counts. Any disallowed portion reduces NIIT only in the later year when the carryforward is finally used.¹¹¹² For a top-bracket borrower, 37% ordinary plus 3.8% NIIT means each deductible dollar of investment interest can be worth more than 40 cents.

Where to Report It

Investment Interest: Form 4952 and Schedule A

Investment interest goes on Form 4952, which reconciles interest paid against NII and computes any carryforward. The allowed amount from line 8 flows to Schedule A (Form 1040), line 9.⁷ Because it is an itemized deduction, the benefit only appears if your total itemized deductions exceed the standard deduction, which is $16,100 for single filers and $32,200 for joint filers in 2026.⁶

Business and Passive Activity Interest

Business interest bypasses Form 4952 and Schedule A. It is reported on the applicable business schedule: Schedule C for sole proprietors, Schedule E for partnerships and S corporations. Passive activity interest follows other passive expenses on Schedule E and is limited to passive income.³

AMT

Investment interest remains deductible under the Alternative Minimum Tax, but the calculation uses AMT-adjusted figures on a separate Form 4952, and the difference is reported on Form 6251.¹³

One Boundary Worth Knowing

Do not pledge an IRA as collateral for an SBLOC. Using an IRA to secure any loan is a prohibited transaction, and the consequence is that the entire IRA is treated as distributed on the first day of the year of the violation. The full fair market value becomes taxable income, and if you are under 59½, an additional early distribution penalty may apply.¹⁴ Most brokerages will not permit this arrangement in the first place, but the penalty is severe enough that it is worth confirming only taxable accounts back the loan.

1
Internal Revenue Service. Publication 550 (2025), Investment Income and Expenses
2
eCFR. 12 CFR Part 221 – Credit by Banks and Persons Other Than Brokers or Dealers for the Purpose of Purchasing or Carrying Margin Stock
3
Office of the Law Revision Counsel. 26 USC 163 – Interest
4
Office of the Law Revision Counsel. 26 USC 469 – Passive Activity Losses and Credits Limited
5
Internal Revenue Service. Real Estate (Taxes, Mortgage Interest, Points, Other Property Expenses)
6
Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
7
Internal Revenue Service. Form 4952, Investment Interest Expense Deduction
8
Office of the Law Revision Counsel. 26 USC 265 – Expenses and Interest Relating to Tax-Exempt Income
9
Office of the Law Revision Counsel. 26 USC 263 – Capital Expenditures
10
eCFR. 26 CFR 1.163-8T – Allocation of Interest Expense Among Expenditures (Temporary)
11
eCFR. 26 CFR 1.1411-4 – Definition of Net Investment Income
12
Internal Revenue Service. 2025 Instructions for Form 8960 – Net Investment Income Tax
13
Internal Revenue Service. Instructions for Form 6251 (2025)
14
Internal Revenue Service. Retirement Topics – Prohibited Transactions