What Types of Interest Are Tax-Deductible?

The types of interest that are tax deductible fall into a short list: home mortgage interest, student loan interest, business interest, rental property interest, and investment interest. Everything else the tax code treats as personal interest, and personal interest is not deductible. What controls the answer is almost never the label on the loan. It’s what you did with the borrowed money.

That distinction matters both ways. Claim interest you weren’t entitled to and the IRS can add a 20% accuracy-related penalty to the underpaid tax.¹ Miss a legitimate deduction and you pay more tax than you owe.

Home Mortgage Interest

Interest on a mortgage secured by your main home or a second home is deductible if you itemize on Schedule A. For mortgages taken out after December 15, 2017, the deduction covers interest on up to $750,000 of debt ($375,000 if married filing separately) used to buy, build, or substantially improve the home. Older mortgages keep the higher $1 million cap ($500,000 if married filing separately).²

These limits were set to expire after 2025 under the Tax Cuts and Jobs Act. The One, Big, Beautiful Bill Act made the $750,000 cap permanent.²

You only benefit if your total itemized deductions clear the standard deduction, which for 2026 is $16,100 for single filers and $32,200 for married couples filing jointly.³

Home Equity Loans and HELOCs

A home equity loan or line of credit produces deductible interest only when the proceeds went to buy, build, or substantially improve the home securing the loan. Use a HELOC to pay off credit cards, take a vacation, or cover any other personal spending and the interest is not deductible, regardless of when you borrowed. This restriction is now permanent.²

Home equity debt also counts against the same $750,000 (or grandfathered $1 million) ceiling as your primary mortgage. It doesn’t get its own bucket.

Student Loan Interest

You can deduct up to $2,500 a year in interest paid on qualified student loans, and you do not have to itemize. The student loan interest deduction is an above-the-line adjustment that reduces adjusted gross income directly, so you get it even when you take the standard deduction.⁴

The deduction phases out at higher incomes. For 2025, single filers start losing it when modified adjusted gross income passes $85,000 and lose it entirely at $100,000. For married couples filing jointly, the phase-out runs from $170,000 to $200,000. Both ranges adjust annually for inflation.⁵

Two filing situations disqualify you outright. You cannot claim the deduction if you file married filing separately, and you cannot claim it if someone else is entitled to list you as a dependent.⁴ The second rule catches many recent graduates whose parents still claim them.

Your loan servicer sends Form 1098-E if you paid $600 or more in interest during the year.⁶ Under $600, no form arrives automatically, but you can still deduct what you actually paid.

Business Interest

Interest on debt used in your trade or business is generally deductible, subject to a cap under Section 163(j). Your deductible business interest for the year cannot exceed your business interest income plus 30% of your adjusted taxable income.⁷

For tax years beginning after December 31, 2024, adjusted taxable income is calculated by adding back depreciation, amortization, and depletion. That produces a larger ATI, and a larger deduction ceiling, than under the 2022–2024 rules.⁷

Small businesses avoid the cap entirely. If average annual gross receipts over the prior three tax years were $31 million or less (the 2025 inflation-adjusted threshold), Section 163(j) does not apply to you. Any business interest disallowed by the 30% cap carries forward to future years.⁷

Rental Property Interest

Mortgage interest on a rental property is deductible as a rental expense on Schedule E, not as an itemized deduction. The $750,000 debt limit that applies to a personal residence does not apply here.² A $900,000 mortgage on a rental produces fully deductible interest.

Watch the passive activity loss rules. If you don’t materially participate in managing the rental, your total rental deductions, interest included, can be limited by those rules.

Investment Interest

If you borrow to buy investments such as stocks, taxable bonds, or land held for appreciation, the interest is deductible as investment interest expense, but only up to your net investment income for the year. Net investment income includes ordinary dividends, interest, royalties, and short-term capital gains from investment property.⁸

Anything over that ceiling carries forward. You compute the deduction and any carryforward on Form 4952, then move the result to Schedule A.⁸

One boundary is absolute. Interest on debt used to buy or carry tax-exempt investments, such as municipal bonds, is never deductible. Federal law blocks the combination of tax-free income and a deductible cost of borrowing to earn it.⁹

Interest You Cannot Deduct

The default rule in the tax code is that personal interest is not deductible. The categories above are the exceptions; everything else is out.¹⁰ The common items people ask about:

Credit card interest is not deductible unless the card was used only for business and every charge can be traced to a business purpose.
Auto loan interest is not deductible on a personal vehicle. Interest on a vehicle used for business may qualify as a business expense to the extent of business use.
Interest the IRS charges on late or underpaid income taxes is not deductible. For 2026, that rate runs 7% in Q1 and 6% in Q2 for individual underpayments, compounded daily.¹¹

Why the Use of the Money Controls

The IRS applies a tracing rule. What secures the loan and what the lender calls it don’t decide the question. What you spent the borrowed money on does. A personal loan poured into business inventory produces deductible business interest. A home equity loan spent on a cruise produces nothing deductible, even though the house is the collateral.

The practical consequence: keep records that show where loan proceeds went. Bank statements, transfer records, invoices paid from the loaned funds. If a deduction is ever questioned, that paper trail is what protects it.

Where Each Type Gets Reported

Reporting each deduction on the right line matters. The wrong form can delay a refund or generate a notice.

Home mortgage interest goes on Schedule A (Form 1040), lines 8a and 8b. Your lender reports the paid amount on Form 1098.¹²
Student loan interest goes on Schedule 1 (Form 1040), line 21, as an adjustment to income.¹³
Business interest for a sole proprietor goes on Schedule C. Partnerships and S corporations report it on their own returns.¹³
Investment interest is computed on Form 4952 and carried to Schedule A, line 9.⁸
Rental property interest goes on Schedule E.²

Every category above is defined by what the borrowed money was used for. Match the use to the category, deduct it on the right form, and keep the records that prove the match.

1
Office of the Law Revision Counsel. 26 U.S. Code 6662 – Imposition of Accuracy-Related Penalty on Underpayments
2
Internal Revenue Service. Publication 936 (2025), Home Mortgage Interest Deduction
3
Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026, Including Amendments From the One, Big, Beautiful Bill
4
Internal Revenue Service. Topic No. 456, Student Loan Interest Deduction
5
Internal Revenue Service. Publication 970 (2025), Tax Benefits for Education
6
Internal Revenue Service. Instructions for Forms 1098-E and 1098-T (2026)
7
Internal Revenue Service. Questions and Answers About the Limitation on the Deduction for Business Interest Expense
8
Internal Revenue Service. Form 4952, Investment Interest Expense Deduction (2025)
9
Office of the Law Revision Counsel. 26 U.S. Code 265 – Expenses and Interest Relating to Tax-Exempt Income
10
Office of the Law Revision Counsel. 26 U.S.C. 163 – Interest
11
Internal Revenue Service. Quarterly Interest Rates
12
Internal Revenue Service. Instructions for Form 1098 (12/2026)
13
Internal Revenue Service. Topic No. 505, Interest Expense