When you make a business loan payment, only part of it is a tax write-off. The interest is deductible as an ordinary business expense; the principal is not. Writing off business loan payments correctly means splitting each payment into those two pieces and only claiming the interest.
The reason traces back to a basic tax principle. Borrowed money is not taxable income when it lands in your account, because you owe it back. Returning it, therefore, is not an expense that reduces your income. Interest is different: it is the price you pay for using someone else’s money, and the federal tax code treats that price like rent, utilities, or any other cost of doing business.
Why Principal Is Not Deductible
Think about what happens when a lender wires $100,000 into your business account. That cash is not income. You have a matching liability for the same amount, so there is no net gain to tax. When you pay the principal back, the liability shrinks and your equity grows, but nothing touches the income statement. Allowing a deduction for principal would give you a double benefit: untaxed cash coming in, and a tax break for sending it out.
Every payment on an amortizing loan has two components, and your lender’s amortization schedule shows the split for each one. Early payments are usually interest-heavy; later payments shift toward principal. If you run a line of credit or make irregular draws, your bookkeeping needs to track the split transaction by transaction.
This is not a minor bookkeeping point. If you overstate deductions by treating principal as interest, the IRS can assess an accuracy-related penalty of 20% of the underpaid tax when the mistake amounts to a substantial understatement, generally defined as an understatement exceeding the greater of 10% of the correct tax or $5,000.1Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty on Underpayments
How the Interest Deduction Works
Federal law allows a deduction for all interest paid or accrued during the tax year on business debt.2Office of the Law Revision Counsel. 26 USC 163 – Interest That covers term loans, lines of credit, equipment financing, commercial mortgages, and most other borrowing tied to your business. The deduction reduces taxable income dollar-for-dollar, so it shields earnings from the 21% corporate rate or individual rates that run up to 37%.3Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
When you claim the deduction depends on your accounting method. Cash-method businesses deduct interest in the year they actually pay it. Accrual-method businesses recognize interest as it accrues, whether or not the check has gone out.4Internal Revenue Service. Publication 538 – Accounting Periods and Methods For most small businesses on cash accounting, the year-end statement from the lender is what goes on the return.
Fees That Count as Interest
The cost of borrowing is not just the stated rate. Origination fees and points that a lender charges for the use of money, rather than for a specific service such as an appraisal, are treated as interest for tax purposes. You generally cannot deduct the full fee in year one. Instead, you amortize it over the life of the loan. A $6,000 origination fee on a five-year loan produces a $1,200 deduction each year.
Prepayment penalties work differently. If you pay off a loan early and the lender charges a penalty for doing so, that penalty is generally deductible as interest in the year you pay it, because the IRS treats it as extra compensation for the use of borrowed money.5Internal Revenue Service. PLR 200011059 – Prepayment Penalties There is no life-of-loan left to spread it over.
Refinancing can accelerate unamortized fees from the old loan into deductions in the year of the refinance, provided the new loan is materially different from the old one. The fresh fees on the new loan then start their own amortization.
When Interest Must Be Capitalized Instead
Not all business interest gets an immediate write-off. If you borrow to produce real property or certain long-lived assets, the interest incurred during the production period must be capitalized. That means it gets added to the cost basis of the asset and recovered over time through depreciation, rather than deducted in the year paid.6Office of the Law Revision Counsel. 26 USC 263A – Capitalization and Inclusion in Inventory Costs of Certain Expenses
The rule applies to what the IRS calls designated property: real property you produce (such as a warehouse or office you are building), tangible personal property with a class life of 20 years or more, property with an estimated production period over two years, and property costing over $1 million with a production period exceeding one year.7eCFR. 26 CFR 1.263A-8 – Requirement to Capitalize Interest
There is a de minimis exception when the production period is 90 days or less. For most small businesses financing off-the-shelf equipment or a vehicle, this rule never comes up. It mostly bites construction projects and custom-built assets.
The Section 163(j) Cap on Large Businesses
Section 163(j) limits business interest deductions in a given year to business interest income plus 30% of adjusted taxable income. For tax years beginning after 2024, adjusted taxable income is calculated on a basis similar to EBITDA, which is more generous than the EBIT-style calculation that applied from 2022 through 2024. Disallowed interest carries forward.8Internal Revenue Service. Questions and Answers About the Limitation on the Deduction for Business Interest Expense
Most small businesses are exempt. If your average annual gross receipts over the prior three years are $32 million or less for 2026, the cap does not apply.9Internal Revenue Service. Revenue Procedure 2025-32 – Inflation Adjustments for 2026 That threshold moves with inflation each year. Businesses above the threshold report the calculation on Form 8990.10Internal Revenue Service. Instructions for Form 8990
Mixed Business and Personal Borrowing
If you use the same loan or credit card for both business and personal spending, only the interest tied to business purchases is deductible. The IRS expects tracing: you follow where the borrowed dollars actually went and allocate the interest based on the ratio of business to total spending on that account.
The cleanest fix is separation. A dedicated business credit card or a standalone business loan eliminates the tracing exercise and makes the deduction defensible in an audit. When separation is not possible, save receipts and document the business purpose for every charge. Rough estimates will not hold up.
Tracing can also work in your favor. A personal loan whose proceeds go entirely into business operations can produce a business interest deduction, because what matters is how the money is used, not the label on the loan. Keep records showing the funds moved directly from the loan account into business expenses.
Loans From Owners and Related Parties
Loans between a business and its owners face extra scrutiny. A shareholder who lends money to an S corporation, for example, needs to establish a real debtor-creditor relationship before the interest is deductible by the business. The IRS looks for a written loan agreement, a stated interest rate, a maturity date, and evidence that repayments are actually being made.11Internal Revenue Service. Valid Shareholder Debt Owed by S Corporation An undocumented advance from a founder can be recharacterized as an equity contribution, which kills the interest deduction entirely.
Rates matter too. If a loan between related parties carries a rate meaningfully below the applicable federal rate, federal law treats the arrangement as if interest were being charged at that minimum rate.12Office of the Law Revision Counsel. 26 USC 7872 – Treatment of Loans With Below-Market Interest Rates The lender is treated as receiving imputed interest income they must report. A market-rate note from the start avoids the whole mess.
When Business Debt Is Forgiven
The principal-is-not-income rule flips when a lender writes off what you owe. If part or all of a business debt is forgiven, the canceled amount is generally taxable income, because you received the cash tax-free and no longer have to give it back.13Internal Revenue Service. Publication 4681 – Canceled Debts, Foreclosures, Repossessions, and Abandonments Sole proprietors report it on Schedule C. The lender will issue Form 1099-C for any canceled debt of $600 or more.14Internal Revenue Service. Instructions for Forms 1099-A and 1099-C
Several exclusions can reduce or eliminate the hit. Debt discharged in a Title 11 bankruptcy is excluded from income. Insolvent taxpayers can exclude canceled debt to the extent their liabilities exceeded the fair market value of their assets immediately before the cancellation. Qualified real property business debt secured by and used to acquire business real property may also be excluded, subject to limits tied to the property’s value and depreciable basis.
Each exclusion carries a cost: you have to reduce tax attributes such as net operating losses or the basis of your assets by the excluded amount. Both the exclusion and the attribute reduction go on Form 982.15Internal Revenue Service. About Form 982 – Reduction of Tax Attributes Due to Discharge of Indebtedness Cash-method taxpayers get one additional break: if paying the debt would have produced a deduction (for example, accounts payable to a vendor), the cancellation does not create income.13Internal Revenue Service. Publication 4681 – Canceled Debts, Foreclosures, Repossessions, and Abandonments
Records to Keep
The interest deduction is only as strong as its paper trail. For every business loan, hold on to the signed loan agreement showing amount, rate, repayment terms, and default consequences; the amortization schedule that breaks each payment into principal and interest; bank statements proving the payments were made and that loan proceeds went to business uses; and the year-end lender statement summarizing interest paid.16Internal Revenue Service. Topic No. 453 – Bad Debt Deduction
Businesses subject to Section 163(j) have additional reporting on Form 8990, which tracks business interest expense, business interest income, and adjusted taxable income across entity types, including passthroughs.10Internal Revenue Service. Instructions for Form 8990 Businesses claiming the small-business exemption should still keep records sufficient to prove they meet the gross receipts threshold if the IRS asks.