Whether line of credit interest is tax deductible depends on what you did with the borrowed money, not on what kind of loan you took out or what collateral you pledged. Federal law disallows deductions for personal interest but carves out exceptions for funds spent on a business, a qualifying home improvement, or a taxable investment.1Office of the Law Revision Counsel. 26 USC 163 – Interest Draw on a line of credit to pay off credit cards, take a vacation, or cover groceries, and the interest is not deductible. Draw on the same line to buy business inventory or renovate the home securing the loan, and it usually is.
The Rule That Controls Everything: Interest Tracing
The IRS follows the money. Under Treasury Regulation 1.163-8T, every borrowed dollar is traced to the specific expenditure it funds, and the interest on that dollar is categorized based on how it was spent. Pledge stock as collateral for a loan but use the cash to buy a personal car, and the interest is personal and non-deductible even though the collateral is an investment asset.2CCH AnswerConnect. Tracing Rules – Allocation of Interest Expenses
This matters most when one credit line funds several purposes. Draw $80,000 to renovate a kitchen and another $20,000 to pay off personal debt, and only the interest on the $80,000 portion may qualify. You need records tying each withdrawal to a specific invoice, receipt, or purchase agreement so the split can be verified. Commingle funds without documentation, and even legitimately deductible interest can be disallowed in an audit.
Borrowing for Business
Interest on money borrowed for business purposes is generally deductible as an ordinary and necessary business expense. Ordinary means common in your industry; necessary means helpful and appropriate for the work. That standard comes from the final edition of IRS Publication 535, which remains the governing guidance.3Internal Revenue Service. Publication 535 – Business Expenses
Typical deductible uses include buying inventory, covering payroll, purchasing equipment, or funding marketing. Interest on a line of credit used to pay the owner’s personal mortgage doesn’t qualify even if the credit line sits in the business’s name. Tracing rules apply with full force: the deduction follows the expenditure, not the borrower.
The Section 163(j) Cap
Businesses with heavy interest expense face a separate ceiling. Deductible business interest in any year generally cannot exceed the business’s interest income plus 30% of its adjusted taxable income. Any excess carries forward.4Internal Revenue Service. Questions and Answers About the Limitation on the Deduction for Business Interest Expense
Small businesses are exempt if their average annual gross receipts over the prior three years fall below an inflation-adjusted threshold. For 2025, that threshold was $31 million, and the IRS adjusts it annually. Most sole proprietors and small LLCs drawing on a credit line for routine expenses will never hit the cap.
Home Equity Lines of Credit
Interest on a HELOC is deductible only when the funds are used to buy, build, or substantially improve the home that secures the loan. Use the same HELOC to consolidate credit card debt, pay tuition, or cover medical bills, and the interest is entirely non-deductible.5Internal Revenue Service. Real Estate (Taxes, Mortgage Interest, Points, Other Property Expenses) 2 The One, Big, Beautiful Bill Act of 2025 made this restriction permanent; it no longer has a sunset date.6Office of the Law Revision Counsel. 26 USC 163 – Interest – Section (h)(3)(F)
“Substantially improve” means work that adds value to the home, extends its useful life, or adapts it to a new use. A full kitchen remodel, a new roof, or converting a garage into living space all qualify. Routine maintenance like repainting or fixing a leaky faucet does not.7Internal Revenue Service. Publication 936 (2025), Home Mortgage Interest Deduction
The $750,000 Debt Ceiling
Total mortgage debt, including primary mortgage and HELOC combined, cannot exceed $750,000 for most filers, or $375,000 for married individuals filing separately. Only interest on debt up to that ceiling is deductible. If your existing mortgage balance is $600,000 and you draw $200,000 on a HELOC for a qualifying renovation, $50,000 of the HELOC balance sits above the cap, and interest on that excess portion is non-deductible.6Office of the Law Revision Counsel. 26 USC 163 – Interest – Section (h)(3)(F)
You Have to Itemize
HELOC interest is deductible only if you itemize on Schedule A instead of taking the standard deduction. For 2026, the standard deduction is $32,200 for married couples filing jointly, $16,100 for single filers, and $24,150 for heads of household.8Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026, Including Amendments From the One, Big, Beautiful Bill If your itemized deductions don’t exceed the standard deduction, the HELOC interest deduction has no practical value. Run the numbers both ways before assuming you’ll benefit.
Second Homes
A HELOC secured by a second home can produce deductible interest if the funds go toward buying, building, or substantially improving that property. You must actually use it as a home; if you rent it out part of the year, you need to personally use it for the longer of 14 days or 10% of the days it was rented at a fair price. The $750,000 cap applies to combined debt across both homes.7Internal Revenue Service. Publication 936 (2025), Home Mortgage Interest Deduction
Borrowing for Investments
When you borrow to buy taxable investments such as stocks, bonds, or non-residential real estate, the interest qualifies as investment interest under Section 163(d). The deduction is capped at your net investment income for the year.9Office of the Law Revision Counsel. 26 USC 163 – Interest – Section (d)
Net investment income generally includes interest, non-qualified dividends, and short-term capital gains from investment property. Long-term capital gains and qualified dividends are excluded by default because they’re taxed at lower rates. Any investment interest expense above your net investment income carries forward to future tax years until you have enough investment income to absorb it.10Office of the Law Revision Counsel. 26 USC 163 – Interest – Section (d)(2)
Margin interest from a brokerage account is treated the same way. One critical exception: using borrowed money to purchase or hold tax-exempt securities like municipal bonds kills the deduction entirely under Section 265.11Office of the Law Revision Counsel. 26 USC 265 – Expenses and Interest Relating to Tax-Exempt Income
Uses That Never Produce a Deduction
Interest is non-deductible when the borrowed money pays for personal consumption. Consolidating credit card balances, paying tuition, covering medical bills, buying a personal vehicle, taking a vacation, or covering everyday living expenses all fall on the personal side of the tracing rule, regardless of what secures the loan. A HELOC used for these purposes produces no deduction, and neither does a business-labeled credit line drawn on to pay the owner’s personal expenses.
Records You Need to Keep
For HELOCs, lenders typically issue Form 1098 if you paid more than $600 in interest during the year.12Internal Revenue Service. About Form 1098, Mortgage Interest Statement Business and investment credit lines usually don’t generate a 1098, so you’ll rely on year-end or monthly statements showing interest paid.
The heavier lift is on tracing. Keep a ledger tying every withdrawal to a specific purpose: contractor invoice, equipment receipt, brokerage confirmation, closing document. If a single credit line funds multiple purposes, log each draw separately with date, amount, and destination. Without that paper trail, even valid deductions can fail on audit.
Where to Report Each Type of Interest
Each category of deductible interest lands on a different form, all feeding into Form 1040:
- Home improvement interest: Schedule A, line 8a if reported on Form 1098, or line 8b if not.
- Business interest for sole proprietors: Schedule C.
- Rental property interest: Schedule E.
- Investment interest: Schedule A, line 9, after completing Form 4952.
Form 4952 is required whenever you claim investment interest, with one narrow exception. You can skip it if your investment income from interest and ordinary dividends (excluding qualified dividends) exceeds your investment interest expense, you have no other deductible investment expenses, and you have no carryforward from prior years.14Internal Revenue Service. Form 4952 (2025) Investment Interest Expense Deduction Anyone carrying forward excess investment interest from a prior year must file the form regardless.
Penalties for Deducting Interest You Shouldn’t
Reclassifying personal interest as business or home improvement interest is not a harmless error. If the IRS finds the mistake came from negligence or a substantial understatement of tax, the accuracy-related penalty is 20% of the underpaid amount.15Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty on Underpayments A substantial understatement generally means the underpayment exceeds the greater of 10% of the correct tax or $5,000.
If the IRS can show the incorrect deduction was intentional, the fraud penalty rises to 75% of the underpayment attributable to fraud.16Office of the Law Revision Counsel. 26 USC 6663 – Imposition of Fraud Penalty Once the IRS establishes any portion of the underpayment was fraudulent, the burden shifts to you to prove the rest was not. Good records are the most practical defense in either case.