Debt basis is the second basis account an S corporation shareholder keeps alongside stock basis, and it exists only for money the shareholder has personally and directly lent to the corporation. Under IRC Section 1366(d), a shareholder can deduct pass-through losses only up to the total of stock basis plus debt basis; anything beyond that is suspended and carried forward. The rule matters to anyone running an S corporation through lean years, including creators and consultants who elected S status and then funded payroll and software out of personal savings.
How debt basis is created, used, and restored
Only bona fide indebtedness running directly from the shareholder to the corporation creates debt basis (Treas. Reg. Section 1.1366-2). Wire $50,000 from your personal account to the company as a documented loan and you have $50,000 of debt basis. Personally guarantee the company's $50,000 bank line and you have zero, no matter how real the exposure feels; a guarantee produces basis only if the bank actually collects from you and you step into the lender's shoes. Loans routed through your other entities do not count either: the debt must run from you personally. A back-to-back arrangement, where you borrow from a bank in your own name and then lend the proceeds to the corporation under your own note, does work if it is genuinely papered and the cash actually moves. What holds up on audit is substance: a written note, a stated interest rate, a repayment schedule, and traceable transfers.
The ordering rules run the same way every year. Income items increase stock basis first, then distributions reduce stock basis, then losses reduce stock basis to zero before they touch debt basis. Once losses have eaten into debt basis, later years' net income restores debt basis first, back up to the loan's face amount, before any of it rebuilds stock basis. Shareholders who claim a loss, receive a distribution, receive a loan repayment, or dispose of stock must attach Form 7203 to their Form 1040 to show the math.
Repayments of a reduced-basis loan are taxable
If the corporation repays a shareholder loan while the loan's basis sits below its face amount, part of every payment is gain. The taxable fraction is the basis reduction divided by the face amount, applied to each repayment. When the loan is evidenced by a written note held more than a year, that gain is long-term capital gain; an open account balance produces ordinary income instead, and open account debt over $25,000 at year end is treated like a note under the regulations. This is the trap that catches owners who quietly pay themselves back in a profitable year after deducting losses against the loan in the bad ones.
2026 figures
Debt basis itself has no indexed dollar amounts. The figures that surround it for 2026: the $25,000 open account debt line in Treas. Reg. Section 1.1366-2 is fixed, not inflation-adjusted. Losses that clear the basis gate must still pass the at-risk rules and the excess business loss limitation, whose thresholds were $313,000 for single filers and $626,000 for joint filers in 2025 (indexed annually, and made permanent by the 2025 legislation). Capital gain recognized on repayment of a reduced-basis note is taxed at the 0%, 15%, or 20% long-term rates, plus the 3.8% net investment income tax where the shareholder's income exceeds $200,000 ($250,000 married filing jointly).
For creators and the self-employed
The typical fact pattern: a creator or consultant elects S corporation status, revenue dips or a big investment year arrives, and the owner covers editors, contractors, and software from personal funds. If that money goes in as a documented loan, the K-1 losses from Form 1120-S stay deductible after stock basis runs out. If it goes in as informal transfers, or as a personal credit card quietly paying company bills, the deduction becomes a documentation fight.
There is also a choice to make before the cash moves: contribution or loan. A capital contribution increases stock basis, supports losses just as well, and never triggers repayment gain, but getting the money back out follows the distribution rules. A loan keeps a clean path to repayment, at the price of the reduced-basis gain trap and the paperwork burden. Either way, basis should be tracked every single year, profitable ones included; reconstructing a decade of basis when the IRS asks is slow, expensive, and often ends with disallowed losses.
Mistakes that cost money
First, counting a personal guarantee as basis. On audit the loss is disallowed, and the bill arrives with interest and accuracy penalties on top of the tax. Second, repaying shareholder loans right after loss years. A $20,000 repayment on a note whose basis was cut in half is $10,000 or more of taxable gain nobody budgeted for. Third, lending on open account past $25,000. Sloppy running balances convert what could have been capital gain treatment into ordinary income and make the year-end netting rules unpredictable. Fourth, skipping Form 7203 and the basis schedule. Missing forms invite IRS notices, and losses claimed without basis support are the first thing an examiner removes. Fifth, lending from the wrong pocket. Money advanced by your other LLC or by a family member creates no debt basis for you, even though the corporation got the cash.
Restoring basis before repayment
Timing a repayment matters because basis restoration happens with the year's income before repayments are measured against it. If the corporation expects a profitable year, letting that income restore debt basis to face value before the note is repaid can shrink or eliminate the gain entirely. The same dollars, paid a year apart, can produce completely different tax results.
If you have lent your S corporation money, or you are about to, have a professional paper the note properly in the year it happens and update Form 7203 annually; these rules reward documentation created at the time, not reconstructed later.