What Is Business Interest Income and How Is It Taxed?

Business interest income is the interest your company earns from lending money or holding interest-bearing assets connected to its trade or business — money-market balances, certificates of deposit, notes receivable, customer installment contracts, and similar instruments. It is ordinary taxable income to the business, and it also raises the ceiling on how much business interest expense the company can deduct in the same year.

What Counts as Business Interest Income

Most companies earn some interest without thinking about it. Commercial checking and savings balances accrue interest daily, and certificates of deposit held in the company’s name generate more on surplus cash. The amounts are often small, but they are taxable and need to be tracked.

Lending and customer transactions produce the rest. When your company extends a loan to an employee or an affiliated entity, the interest on that note is business interest income. Installment sale contracts, where a buyer pays off a purchase over time, generate steady interest revenue. Late-payment charges on overdue invoices count too: if your sales contract carries a penalty rate for missed deadlines, those charges are interest income to the business.

Any bank or financial institution that pays your business $10 or more in interest during the year must send a Form 1099-INT reporting the amount.¹ You still owe tax on interest below that threshold or interest a payer wasn’t required to report. Leaving small amounts off the return is one of the easier ways to draw a notice, because the IRS matches 1099-INT filings against what taxpayers report.

Trade or Business vs. Personal Investment

Not every dollar of interest a business owner earns qualifies as business interest income. The IRS separates interest tied to active operations from interest on personal investments. To count, the interest must be “properly allocable to a trade or business” — the underlying asset that produces it has to be connected to your company’s operations rather than held for personal investment.²

The regulations give a clean example. A sole proprietor who earns interest on a note receivable from the business has business interest income. If the same person uses personal funds to buy corporate bonds on the side, the interest from those bonds is investment income, not business interest income, even though the individual runs a business.² The classification matters for the interest expense limitation discussed below.

Imputed Interest on Below-Market Loans

If your business lends money to an employee, shareholder, or related party at little or no interest, the IRS may treat the arrangement as if interest had been charged at a fair market rate. That phantom amount is called imputed interest, and it can create taxable income for the lender even when no cash interest was collected.

A “below-market loan” under federal law is any loan carrying an interest rate below the applicable federal rate (AFR) that the IRS publishes each month.³ The AFR is set by loan term: short-term (three years or less), mid-term (over three but not more than nine years), and long-term (over nine years). Charge less than the AFR and the IRS treats the shortfall as additional taxable income to the lender, and, depending on the relationship, as compensation, a distribution, or a gift to the borrower.

A narrow exception applies. Imputed interest rules do not reach compensation-related loans between employer and employee, or corporation-shareholder loans, when the total outstanding balance between the parties is $10,000 or less, unless a principal purpose is tax avoidance.³ Above that threshold, charge at least the current AFR to avoid phantom income.

Original Issue Discount

If your business holds a debt instrument bought for less than its face value, such as a discounted bond or a zero-coupon note, the gap between purchase price and redemption price is original issue discount (OID). The IRS treats OID as a form of interest income that accrues over the life of the instrument, even if no cash payments arrive until maturity.⁴

Brokers and middlemen holding OID instruments for you must file Form 1099-OID when the discount is $10 or more for the year.⁴ A de minimis rule lets you treat the OID as zero if it is less than one-quarter of one percent of the redemption price at maturity multiplied by the full years to maturity. Above that threshold, you include the OID in income as it accrues rather than waiting for redemption.

Where to Report It on Your Return

Where business interest income lands on the return depends on how the company is organized.

Sole proprietorships and single-member LLCs report it on Schedule C (Form 1040), line 6, which covers other income including interest on notes and accounts receivable.⁵
C-corporations report taxable interest on Form 1120, line 5, covering interest on loans, notes, mortgages, bonds, bank deposits, and similar instruments.⁶
Partnerships and multi-member LLCs report it on Form 1065, Schedule K, line 5, with each partner’s share flowing through on Schedule K-1.⁷
S-corporations report it on Form 1120-S, Schedule K, line 4, which then passes through to shareholders on their K-1s.

Tax-exempt interest, for example from municipal bonds held as part of operations, is reported separately. Partnerships disclose it on Schedule K, line 18a, using code A on Schedule K-1.⁷ It is not included in taxable income, but it still has to be shown on the return.

How Interest Income Affects Your Interest Expense Deduction

Business interest income is not just revenue. Under Section 163(j), the amount of business interest expense your company can deduct in a year is capped at the sum of your business interest income, 30 percent of your adjusted taxable income, and any floor plan financing interest.⁸ Interest expense above the cap carries forward to future years.

Companies subject to the limitation show the calculation on Form 8990 and report current-year business interest income on line 23.⁸ More interest income means a higher cap and a larger allowable deduction, which is one reason accurate tracking matters beyond bare reporting.

Smaller companies can skip the exercise. A small business taxpayer whose average annual gross receipts over the prior three years do not exceed $32 million for tax years beginning in 2026 is exempt from the limitation and generally does not file Form 8990.⁹ The statutory base is $25 million, adjusted annually for inflation.¹⁰

The FBAR is due April 15 for the prior calendar year, with an automatic extension to October 15. It is filed electronically through FinCEN’s BSA E-Filing System, not with your federal tax return. Records for each reported account, including account number, bank name, and maximum annual value, must be kept for at least five years from the FBAR’s due date.¹¹

When to Recognize the Income: Cash vs. Accrual

Timing depends on your accounting method. Under the cash method, you record interest only when payment actually arrives. If a customer owes $500 in interest on an installment contract but hasn’t paid, that $500 is not income yet. Many small businesses use cash-basis accounting because it lines taxable income up with actual cash flow.

Under the accrual method, interest is recorded as it is earned, the moment you have a right to the income, even if the check has not come. Larger companies and C-corporations more commonly use accrual. The basic calculation is principal times annual rate, adjusted for the portion of the year the funds were outstanding. Compound arrangements require accounting for interest earned on previously accumulated interest, which grows the total over longer periods.

Penalties for Leaving Interest Off the Return

Missing interest income can be expensive. If the IRS determines you substantially understated your income tax, it can impose an accuracy-related penalty equal to 20 percent of the underpayment. For individuals, a “substantial understatement” is one that exceeds the greater of 10 percent of the tax that should have been shown or $5,000. For corporations other than S-corporations, the threshold is the lesser of 10 percent of the correct tax (or $10,000, whichever is greater) and $10 million.¹²

Where the IRS finds clear and convincing evidence that the omission was intentional, a civil fraud penalty of 75 percent of the underpayment applies.¹³ Small amounts still matter, because the IRS matches its 1099-INT records against what taxpayers report. Reporting every dollar of interest, including amounts under the $10 Form 1099-INT threshold, is the simplest way to stay out of trouble.

1
Internal Revenue Service. About Form 1099-INT, Interest Income
2
eCFR. 26 CFR 1.163(j)-10 – Allocation of Interest Expense, Interest Income, and Other Items
3
Office of the Law Revision Counsel. 26 U.S. Code 7872 – Treatment of Loans With Below-Market Interest Rates
4
Internal Revenue Service. Guide to Original Issue Discount (OID) Instruments
5
Internal Revenue Service. 2025 Instructions for Schedule C (Form 1040)
6
Internal Revenue Service. Instructions for Form 1120 (2025)
7
Internal Revenue Service. Instructions for Form 1065 (2025)
8
Internal Revenue Service. Instructions for Form 8990
9
Internal Revenue Service. Rev. Proc. 2025-32
10
Internal Revenue Service. Report of Foreign Bank and Financial Accounts (FBAR)
12
Office of the Law Revision Counsel. 26 U.S. Code 6662 – Imposition of Accuracy-Related Penalty on Underpayments
13
Internal Revenue Service. Civil Fraud