Indebtedness expenses are the costs you take on when you borrow money, and for federal tax purposes the biggest one is interest. The rest of the family includes loan origination fees (points), original issue discount, bond premium, and certain commitment fees. Whether any of these is deductible, and when, depends less on the loan itself than on what you did with the borrowed funds. That single question, tracing the use of the money, drives almost every rule that follows.
What Counts as an Indebtedness Expense
Section 163(a) of the Internal Revenue Code opens with a broad allowance: interest paid or accrued on indebtedness during the tax year is deductible.1Office of the Law Revision Counsel. 26 USC 163 – Interest The rest of Section 163 then carves that allowance into categories, exceptions, and limits that consume much of the general rule.
Beyond straight interest, the following financing charges also count:
- Loan origination fees, or points, which are upfront charges for arranging a loan and are treated as prepaid interest.
- Original issue discount (OID), the built-in discount when a bond or note is issued below its face value.
- Bond premium, the excess paid above face value when debt is issued above par, which reduces the effective interest cost over time.
- Commitment fees, charges for a lender’s promise to keep funds available, which may be treated as interest depending on the arrangement.
Each has its own timing rule. Points generally spread over the loan term. OID accrues annually. Bond premium offsets interest expense as it is amortized.
The Use of the Money Decides the Treatment
The tax treatment of interest turns on what you did with the loan proceeds, not on what secures the debt. This principle is the interest tracing rule in the Treasury regulations.2eCFR. 26 CFR 1.163-8 – Allocation of Interest Expense Among Expenditures A home equity loan used to buy business inventory produces business interest, even though a house secures it. A personal loan used to buy stocks produces investment interest, not personal interest.
The practical consequence is that you have to track every dollar. Commingling loan proceeds with personal funds in a single account makes tracing hard and often pushes the interest into a less favorable category. Parking borrowed funds in a separate account until you deploy them for a specific purpose is the cleanest way to preserve the classification you want.
The Four Categories of Interest
Once you trace where the money went, the interest falls into one of four categories, each with its own deduction rule. Misclassifying interest across these categories is one of the more common errors on business and individual returns.
Business Interest
Interest on debt used in a trade or business is generally deductible, but most businesses face a cap under Section 163(j). The deductible amount for the year cannot exceed business interest income plus 30% of adjusted taxable income. Any excess carries forward indefinitely.3eCFR. 26 CFR 1.163(j)-2 – Deduction for Business Interest Expense Limited – Section: Disallowed Business Interest Expense Carryforward The mechanics are covered in the Section 163(j) section below.
Investment Interest
Interest on money borrowed to buy or carry investment property is deductible only up to your net investment income for the year. Net investment income means investment income (dividends, non-qualified interest, short-term capital gains, and royalties not from a business) minus investment expenses. Anything above that ceiling carries forward with no expiration and can be deducted whenever you have enough investment income to absorb it.4Office of the Law Revision Counsel. 26 USC 163 – Interest – Section: Limitation on Investment Interest
Qualified dividends and long-term capital gains count as investment income for this calculation only if you elect to treat them as such. That election costs you the preferential rate on those gains, so whether it makes sense depends on your bracket and the amount of interest at stake.
Passive Activity Interest
Interest on debt used to fund a passive activity, typically a rental property or a business you don’t materially participate in, gets folded into the activity’s overall profit-or-loss calculation. If the activity shows a net loss, the passive activity loss rules under Section 469 block the deduction until you either generate passive income elsewhere or dispose of the activity.5Office of the Law Revision Counsel. 26 USC 469 – Passive Activity Losses and Credits Limited The interest itself isn’t separately capped; it’s just one input to the passive loss calculation.
Personal Interest
Anything that doesn’t fit the three categories above is personal interest, and it isn’t deductible. Credit card interest, auto loan interest on a personal vehicle, and interest on loans used for personal expenses all land here.6Office of the Law Revision Counsel. 26 USC 163 – Interest – Section: Disallowance of Deduction for Personal Interest Two exceptions survive.
Qualified residence interest is the first. You can deduct interest on up to $750,000 of mortgage debt ($375,000 if married filing separately) used to buy, build, or substantially improve your main or second home, with the debt secured by that residence.7Internal Revenue Service. Publication 936 (2025) – Home Mortgage Interest Deduction Mortgages taken out before December 16, 2017, keep the higher $1 million cap ($500,000 filing separately). Home equity lines of credit qualify only when the proceeds go toward buying, building, or substantially improving the home securing the loan; using a HELOC to pay off credit cards or fund a vacation makes the interest nondeductible personal interest.8Internal Revenue Service. Real Estate (Taxes, Mortgage Interest, Points, Other Property Expenses) 2
Student loan interest is the second. You can deduct up to $2,500 of interest paid on qualified education loans, even if you don’t itemize. For 2026, the deduction phases out between $85,000 and $100,000 of modified adjusted gross income for single filers, and between $175,000 and $205,000 for joint filers.9IRS. Rev. Proc. 2025-32 – Section: Interest on Education Loans
The Section 163(j) Cap on Business Interest
For businesses above a certain size, Section 163(j) is the single largest constraint on deducting interest.
How the Formula Works
Your allowable business interest deduction equals business interest income, plus 30% of adjusted taxable income, plus any floor plan financing interest (a narrow category mainly relevant to vehicle dealers). Anything above that ceiling is disallowed for the current year.10eCFR. 26 CFR 1.163(j)-2 – Deduction for Business Interest Expense Limited
Adjusted taxable income is the number that moves the deduction most. For tax years beginning in 2026, the calculation uses an EBITDA-style approach: start with taxable income and add back depreciation, amortization, and depletion. That add-back was not available from 2022 through 2024, when the cap was effectively much tighter. Its restoration permanently increases the interest that most capital-intensive businesses can deduct.
The Small Business Exemption
The entire limitation is irrelevant if your business qualifies as a small business taxpayer. For tax years beginning in 2026, that means average annual gross receipts of $32 million or less over the three preceding tax years.11IRS. Rev. Proc. 2025-32 – Section: Limitation on Use of Cash Method of Accounting Related entities must be aggregated for this calculation, and tax shelters are ineligible regardless of size.12eCFR. 26 CFR 1.163(j)-2 – Deduction for Business Interest Expense Limited – Section: Small Business Exemption
Real property trades or businesses and farming businesses can also elect out entirely, but the price is using the alternative depreciation system (a slower method) for their real or farm property.
What Happens to Disallowed Interest
Business interest above the cap carries forward indefinitely and gets retested each year against a fresh version of the formula.3eCFR. 26 CFR 1.163(j)-2 – Deduction for Business Interest Expense Limited – Section: Disallowed Business Interest Expense Carryforward Partnerships are more complicated: disallowed amounts pass through as “excess business interest expense” to individual partners, and each partner can only deduct it when that same partnership later generates enough income to absorb it.
Points, Original Issue Discount, and Bond Premium
Not every borrowing cost is straight interest. The fees and pricing adjustments around a debt issuance have their own timing rules.
Points
Points paid to secure a mortgage or other loan are prepaid interest. The default rule spreads the deduction ratably over the loan’s life rather than allowing a full upfront deduction.13Internal Revenue Service. Topic No. 504 – Home Mortgage Points On a 30-year mortgage, that means dividing the points by 360 monthly payments and deducting based on the number of payments made in the year.14Internal Revenue Service. Real Estate (Taxes, Mortgage Interest, Points, Other Property Expenses) 6
There is one large exception. Points paid on a mortgage to purchase your principal residence can be deducted in full in the year paid, provided you use the cash method and the points meet the usual requirements (paid at closing, within the range customary for the area, and not paid in lieu of other closing costs).13Internal Revenue Service. Topic No. 504 – Home Mortgage Points If you refinance and later pay the loan off early or refinance again with a different lender, any remaining unamortized points can be deducted in that final year.14Internal Revenue Service. Real Estate (Taxes, Mortgage Interest, Points, Other Property Expenses) 6
Original Issue Discount
When a bond or note is issued for less than its face value, the difference between the issue price and the redemption price is original issue discount. OID is economically the same as interest: the borrower received less cash upfront but owes the full face amount at maturity. The issuer accrues and deducts OID over the life of the instrument even when no cash payment is made until maturity, and the holder reports the same accrual as income.
Bond Premium
When debt is issued above face value, the excess is a bond premium and reduces the issuer’s effective interest cost. Instead of deducting the full stated interest each period, the issuer amortizes the premium as a reduction of interest expense over the bond’s life. The net interest deduction each year reflects the true economic cost of the borrowing.
When Interest Must Be Capitalized Instead of Deducted
Some interest cannot be deducted currently even when it otherwise qualifies. Under Section 263A, interest incurred during the production of certain property must be capitalized into the asset’s cost. This applies to assets with a long useful life, assets with an estimated production period longer than two years, or assets costing more than $1 million with a production period longer than one year.15Office of the Law Revision Counsel. 26 USC 263A – Capitalization and Inclusion in Inventory Costs Interest on borrowings used to build a warehouse or construct a ship gets added to the asset’s tax basis and recovered over time through depreciation rather than deducted in the year paid.
Forms You Have to File
Two IRS forms cover the most common indebtedness reporting situations.
Form 8990 is required for any taxpayer with business interest expense, a disallowed business interest carryforward, or current-year excess business interest expense. Partnerships allocating excess taxable income or excess business interest income to partners also file it. Small business taxpayers (average gross receipts of $32 million or less for 2026) are exempt unless they have excess business interest expense from a partnership. Businesses operating exclusively in excepted trades or businesses (real property, farming, regulated utilities, or employee services) also do not have to file.16IRS. Instructions for Form 8990 (Rev. December 2025)
Form 4952 is for individuals claiming a deduction for investment interest expense. You must file it unless all three of these conditions are met: your investment income from interest and ordinary dividends exceeds your investment interest expense, you have no other deductible investment expenses, and you have no prior-year carryover of disallowed investment interest.17IRS. Form 4952 – Investment Interest Expense Deduction
What Misreporting Costs
An incorrect interest deduction that leads to a substantial understatement of income tax can trigger an accuracy-related penalty of 20% of the underpayment.18Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty on Underpayments For a gross valuation misstatement the penalty doubles to 40%. A substantial understatement for individuals generally means the tax reported was off by the greater of 10% of the correct tax or $5,000.
The mistakes that tend to draw the penalty in this area are the same ones the tracing rules are designed to prevent: claiming business interest on a loan whose proceeds actually funded personal use, ignoring the Section 163(j) cap, or failing to capitalize interest under Section 263A. Contemporaneous records of how each loan’s proceeds were spent, and a properly completed Form 8990 when required, are the practical defenses.