Is Interest Tax Deductible? Mortgage, Student Loan, and Business Types

Is interest tax deductible? Some of it is, and some of it isn’t. Federal law lets you deduct interest in four categories: mortgage interest on your home, interest on qualified student loans, investment interest tied to taxable investments, and interest on business borrowing. Personal interest — the kind you pay on credit cards, car loans, and general-purpose personal loans — is not deductible. Whether a deduction you qualify for actually lowers your tax bill often turns on whether you itemize and how much you earn.

Mortgage Interest on Your Home

Interest on a loan secured by your primary home or a second home is deductible if you itemize on Schedule A. The home has to secure the loan, meaning the lender can foreclose if you stop paying, and the property needs sleeping, cooking, and bathroom facilities. Houses, condos, mobile homes, and boats that meet those criteria all count.¹

How much debt qualifies depends on when you borrowed:

Loans taken before December 16, 2017: interest on up to $1 million of mortgage debt ($500,000 if married filing separately).
Loans taken on or after December 16, 2017: interest on up to $750,000 ($375,000 if married filing separately).

These limits apply to the combined balance across your main home and second home, not to each property separately.² Only debt used to buy, build, or substantially improve the home counts.¹

Home Equity Loans and HELOCs

Interest on a home equity loan or line of credit is deductible only if you use the money to buy, build, or substantially improve the home that secures it. When that test is met, the debt is treated as acquisition debt and falls under the same $750,000 or $1 million cap as your first mortgage.³

Use the same HELOC to consolidate credit card debt, pay medical bills, or fund a vacation, and the interest is not deductible. What you spent the money on decides the answer, not the loan’s name.

Student Loan Interest

If you’re repaying a qualified student loan, you can deduct up to $2,500 of interest per year.⁴ This is an above-the-line deduction, so you claim it on Form 1040 whether or not you itemize. Taxpayers who take the standard deduction still get the benefit.⁵

The loan must have paid for qualified education expenses — tuition, room and board, books, supplies, equipment — and the student must have been enrolled at least half-time in a degree program when the loan originated.⁵ The loan can be for you, your spouse, or someone who was your dependent when you took it out.

For the 2026 tax year, the deduction phases out starting at $85,000 of modified adjusted gross income for single filers and $175,000 for joint filers. It’s gone entirely at $100,000 single and $205,000 joint.⁶ You can’t claim it if you file married filing separately, and you can’t claim it if someone else claims you as a dependent.⁵

Investment Interest

When you borrow to buy investments that produce taxable income, such as buying stocks on margin, you can deduct the interest — but only up to your net investment income for the year.⁷ Net investment income includes ordinary dividends, taxable interest, and short-term capital gains. It does not automatically include long-term capital gains or qualified dividends.

You can elect to include long-term gains and qualified dividends in net investment income, which raises your deduction ceiling. The catch: any gains you pull in lose their preferential rate and get taxed as ordinary income.⁸ Run the numbers both ways before making the election, because the lower capital gains rate you give up can cost more than the extra deduction saves.

If your investment interest exceeds your net investment income, the unused amount carries forward to future years indefinitely.⁹ You calculate the deduction on Form 4952, and the deductible portion flows to Schedule A.

Business Interest

Interest on debt used for business operations is generally a deductible business expense. How much you can deduct depends on the size of the business.

Small businesses that average $31 million or less in annual gross receipts over the prior three years are exempt from any cap and can deduct all of their business interest. The threshold adjusts each year for inflation.¹⁰

Larger businesses run into the Section 163(j) limit. Their deductible business interest in a given year can’t exceed the sum of business interest income, 30 percent of adjusted taxable income (ATI), and any floor plan financing interest.¹⁰ Starting in 2025, businesses can once again add back depreciation, amortization, and depletion when calculating ATI, which raises the ceiling compared with the 2022–2024 period when those add-backs weren’t allowed.

Sole proprietors report business interest on Schedule C, where it reduces net business profit directly. Partnerships and corporations use their own returns but apply the same underlying rules. Interest on debt that isn’t tied to a business activity — a personal credit card, a family vacation loan — doesn’t qualify, even if you’re a business owner.

Interest You Can’t Deduct

The IRS specifically prohibits deductions for personal interest, which covers most everyday consumer borrowing:⁷

Credit card interest on personal purchases such as groceries, clothing, or dining out.
Auto loan interest on a car used personally. If the vehicle is used for business, the business-use portion may qualify as a business expense.
Personal loans, when the proceeds go to personal spending rather than a home purchase, qualified education, investment, or business use.

Use, not label, decides the outcome. A personal loan used to renovate your home could qualify under the mortgage rules if the home secures the debt. A business credit card used to buy personal items does not become a business deduction.

Will the Deduction Actually Help You?

Mortgage interest and investment interest only reduce your tax bill if you itemize on Schedule A. Itemizing pays off only when your total itemized deductions beat the standard deduction for your filing status. For the 2026 tax year, the standard deduction is:¹¹

Single: $16,100
Married filing jointly: $32,200
Head of household: $24,150

If your mortgage interest, state and local taxes (capped at $40,400 for most filers in 2026), charitable contributions, and other itemized deductions together fall below your standard deduction, the standard deduction wins. Your interest payments still cost you money; you just don’t get a separate tax benefit that year.

Student loan interest is the exception. Because it’s above the line, you claim it on Form 1040 regardless of whether you itemize, on top of whichever deduction method you use.⁵

1
Internal Revenue Service. Publication 936 (2025), Home Mortgage Interest Deduction
2
Internal Revenue Service. Real Estate Taxes, Mortgage Interest, Points, Other Property Expenses 5
3
Internal Revenue Service. Real Estate Taxes, Mortgage Interest, Points, Other Property Expenses 2
4
Office of the Law Revision Counsel. 26 USC 221 – Interest on Education Loans
5
Internal Revenue Service. Topic No. 456, Student Loan Interest Deduction
6
Internal Revenue Service. Revenue Procedure 2025-32, Tax Year 2026 Inflation Adjustments
7
Internal Revenue Service. Topic No. 505, Interest Expense
8
Internal Revenue Service. Publication 550 (2024), Investment Income and Expenses
9
Internal Revenue Service. About Form 4952, Investment Interest Expense Deduction
10
Internal Revenue Service. Questions and Answers About the Limitation on the Deduction for Business Interest Expense
11
Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026, Including Amendments From the One, Big, Beautiful Bill