Interest on a home equity loan used for business or investment purposes is deductible, but not as mortgage interest. Under Treasury Regulation 1.163-8T, the IRS classifies loan interest by how you actually spend the money, not by what secures the loan. That opens up two deductions that are often more valuable than the Schedule A mortgage interest deduction: a business expense on Schedule C that also reduces self-employment tax, or an investment interest expense on Form 4952. The key is making a deliberate election, tracing the funds cleanly, and reporting the interest in the right place.
How Interest Tracing Works
The rule that makes this whole strategy possible is in Treasury Regulation 1.163-8T, known as the interest tracing rule. Debt is allocated to whatever expenditure the borrowed money actually funds, and the interest on that debt follows the same allocation.1eCFR. 26 CFR 1.163-8T – Allocation of Interest Expense Among Expenditures (Temporary) Your house is irrelevant to the classification. The same $80,000 borrowed against home equity produces business interest if it funds inventory, investment interest if it buys stocks, and nondeductible personal interest if it pays off a credit card.
You do not have to spend the proceeds the day they arrive. IRS Notice 89-35 extended the original safe harbor to 30 days: an expenditure counts as made from debt proceeds if it happens within 30 days before or 30 days after the proceeds are deposited into your account. Money sitting past that window is treated as an investment in the account itself, which reclassifies the interest.
If a single loan funds more than one use, the debt splits proportionally. Borrow $100,000, spend $60,000 on business inventory and $40,000 on a personal boat, and 60% of the interest is business interest while 40% is nondeductible.1eCFR. 26 CFR 1.163-8T – Allocation of Interest Expense Among Expenditures (Temporary) When you pay down a mixed-use debt, the repayment applies first to the personal portion, then to investment and passive activity portions, and last to the business portion. That ordering works in your favor because it wipes out the nondeductible piece first.
Electing Out of Qualified Residence Interest
By default, interest on debt secured by your home may be classified as qualified residence interest, which lands on Schedule A. That deduction is currently capped at interest on $750,000 of acquisition debt ($375,000 if married filing separately), and interest on home equity debt used for anything other than home improvement is not deductible as mortgage interest at all.2Internal Revenue Service. Publication 936 – Home Mortgage Interest Deduction Those limits came from the Tax Cuts and Jobs Act and were originally set to expire after 2025; whether they continue into 2026 depends on congressional action.
Treasury Regulation 1.163-10T lets you elect to treat any debt secured by your home as if it were not secured by a qualified residence.3eCFR. 26 CFR 1.163-10T – Qualified Residence Interest (Temporary) Once you make the election, the tracing rules in 1.163-8T take over and the interest follows the money. Attach a statement to your return for the year you want the election to apply. It does not have to be the year you took on the debt. The election is irrevocable without IRS consent, so make it deliberately.
The election is most valuable when the interest would otherwise be trapped inside the qualified residence caps, or when it would be completely nondeductible under the home equity rules. A sole proprietor who borrowed against home equity to fund operations can shift that interest from a limited (or zero) Schedule A benefit to a full Schedule C deduction.
Deducting Interest on Business Use
When traced proceeds fund a real trade or business, the interest is an ordinary business expense. There are no dollar caps analogous to the qualified residence limits. The IRS does require that the activity be a genuine trade or business pursued with regularity and a profit motive, not a hobby. Buying inventory, purchasing equipment, or covering payroll during a slow month qualifies. An occasional side pursuit without the structure of a real business likely does not.
The reason this deduction usually beats Schedule A treatment: business interest goes on Schedule C above the net profit line. That profit then feeds Schedule SE, so every dollar of interest that lowers Schedule C profit also shaves the 15.3% self-employment tax.4Internal Revenue Service. Schedule SE (Form 1040) – Self-Employment Tax Mortgage interest on Schedule A gets you neither that reduction nor any benefit if you take the standard deduction.
The 163(j) Cap for Larger Businesses
Section 163(j) caps the business interest deduction at 30% of adjusted taxable income plus business interest income and floor plan financing interest.5Internal Revenue Service. Questions and Answers About the Limitation on the Deduction for Business Interest Expense Any excess carries forward. Small businesses are exempt if their average annual gross receipts over the prior three years stay at or below an inflation-adjusted amount, which was $31 million for 2025. Most homeowners tapping equity for a small business fall well below that. For taxable years beginning after 2024, adjusted taxable income is calculated after adding back depreciation, amortization, and depletion, which generally increases the allowable deduction.
Deducting Interest on Investment Use
Proceeds used to buy stocks, bonds, or similar investment assets produce investment interest under Section 163(d). The deduction in any year cannot exceed your net investment income, which means investment income (interest, nonqualified dividends, short-term capital gains) minus investment expenses other than interest.6Office of the Law Revision Counsel. 26 USC 163 – Interest Pay $12,000 in investment interest but earn only $7,000 of net investment income, and your deduction is $7,000. The unused $5,000 carries forward indefinitely and can be used in any later year with enough investment income to absorb it.
Electing to Include Qualified Dividends and Long-Term Gains
Qualified dividends and long-term capital gains normally get preferential rates (0%, 15%, or 20%) and stay out of the net investment income calculation. You can elect to include them, which raises your investment interest ceiling, but those amounts then lose the preferential rate and get taxed as ordinary income. The trade only makes sense when the carryforward is large and you doubt you will use it in future years.
Tax-Exempt Bonds Break the Deduction
One hard prohibition: if borrowed funds are used to buy tax-exempt bonds, typically municipals, the interest on that debt is entirely nondeductible under Section 265.7Office of the Law Revision Counsel. 26 USC 265 – Expenses and Interest Relating to Tax-Exempt Income The statute’s “incurred or continued” language means even keeping an existing loan outstanding while holding tax-exempt bonds can trigger the disallowance.
The Net Investment Income Tax Benefit
High-income taxpayers also pay a 3.8% Net Investment Income Tax on the lesser of net investment income or the amount by which modified adjusted gross income exceeds a filing-status threshold ($250,000 joint, $200,000 single, $125,000 married filing separately). Those thresholds are not indexed for inflation.8Internal Revenue Service. Net Investment Income Tax The deductible investment interest from Form 4952 flows to Form 8960 and reduces the income subject to the 3.8% surtax.9Internal Revenue Service. Instructions for Form 8960 The same interest classified as mortgage interest on Schedule A gives you no such offset.
Passive Activity and At-Risk Limits Can Still Block the Deduction
A valid trace does not guarantee a current deduction. Two additional filters can delay or disallow it.
Section 469’s passive activity loss rules prevent you from using losses from a business in which you do not materially participate to offset wages, portfolio income, or other nonpassive income.10Office of the Law Revision Counsel. 26 USC 469 – Passive Activity Losses and Credits Limited Traced interest becomes part of that activity’s net result, and if the activity shows a loss, the loss is suspended until you have passive income to absorb it or you dispose of the entire activity. Rental real estate has a $25,000 allowance for active participants with modified adjusted gross income under $100,000, phasing out completely at $150,000.
Section 465’s at-risk rules cap deductible losses at what you personally stand to lose. Borrowed amounts count only if you are personally liable or have pledged property outside the activity as security.11Office of the Law Revision Counsel. 26 USC 465 – Deductions Limited to Amount at Risk A home equity loan pledged as collateral for business funds usually clears this test because your residence is outside the business activity.
Refinancing Carries the Trace Forward
Refinancing does not reset the classification. New debt that replaces existing debt inherits the traced character of the original, up to the principal balance being refinanced. If $60,000 of your original loan was traced to your business, $60,000 of the refinanced loan keeps that business classification. Any additional cash-out amount gets its own trace based on how you spend those new proceeds. Problems arise when refinancing commingles the old balance with new money and records do not separate the two. If you cannot show which portion replaced the business-traced debt, the IRS may treat the whole thing as personal.
Documentation Is the Whole Ballgame
Deposit loan proceeds into a dedicated account that holds nothing else. Commingling with personal funds creates an allocation problem that the ordering rules can sometimes solve but never as cleanly as a separate account. Keep the loan disbursement letter showing the amount and funding date, invoices or receipts for what you bought, and, for business use, bookkeeping entries reflecting the capital contribution or loan on the entity’s balance sheet. For investments, brokerage statements showing the deposit and the subsequent purchases close the loop.
Sloppy records risk more than reclassification. They can trigger the 20% accuracy-related penalty for negligence or a substantial understatement of income.12Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty on Underpayments
Where the Deduction Goes on Your Return
The form depends entirely on the traced use:
- Business use as a sole proprietor: interest goes on the interest expense line of Schedule C. Net profit flows to Schedule 1 for income tax and to Schedule SE for self-employment tax.13Internal Revenue Service. Schedule C (Form 1040) – Profit or Loss From Business
- Rental property or partnership interest: report on Schedule E.
- Investment use: complete Form 4952 to calculate the allowable amount, and carry the deductible portion to Schedule A, line 9. You may skip Form 4952 only if your investment income from interest and ordinary dividends exceeds your investment interest expense, you have no other deductible investment expenses, and you carry no disallowed investment interest from a prior year.14Internal Revenue Service. Form 4952 – Investment Interest Expense Deduction
Expect a discrepancy with your Form 1098. The lender reports total mortgage interest on the loan as a single figure with no breakdown by use.15Internal Revenue Service. About Form 1098 – Mortgage Interest Statement When you split the interest across schedules, none of the individual amounts will match the 1098 total. That is correct, but you need a worksheet in your records showing exactly how you allocated the interest based on the traced use of funds.