How to Report Ordinary Business Income (Loss) on a K-1

To report ordinary business income or loss from a K-1, you carry the Box 1 amount from your Schedule K-1 to Schedule E of Form 1040 and pay tax on it at your ordinary income rates. Partnership and LLC K-1s go on Schedule E, Part II; S-corporation K-1s go on Part III.1Internal Revenue Service. About Schedule E (Form 1040), Supplemental Income and Loss From there the total flows through Schedule 1 to your 1040. That’s the mechanical answer. The substantive answer depends on three things: whether Box 1 is a gain or a loss, what type of entity issued the K-1, and how active you are in the business.

Enter Box 1 Exactly As Reported

The IRS matches the Box 1 figure on your return against the K-1 the entity filed with its Form 1065 or Form 1120-S using its Automated Underreporter system.2Internal Revenue Service. Automated Underreporter (AUR) PIA If the numbers don’t line up, a notice follows. Enter Box 1 exactly as printed, even if you believe it’s wrong. If the K-1 itself is incorrect, the entity has to issue a corrected one; you do not adjust the number on your own return.

Once Box 1 is on Schedule E, it combines with any other pass-through income and is taxed alongside your wages, interest, and other ordinary income at your marginal rate. That’s the endpoint for a straightforward profit year. Everything else in this article is about what happens around that number.

What Box 1 Contains, and What It Doesn’t

Box 1 is the net operating result of the entity’s core trade or business: revenue minus ordinary costs. It does not include items the tax code requires you to handle individually. Those “separately stated” items sit in other boxes so the right rules apply on your return:

If Box 1 looks small compared to what you know the business earned, the difference is usually sitting in these other boxes. Each one goes to a different place on your return.

Self-Employment Tax on Box 1

Whether the Box 1 amount is hit with self-employment tax depends on the entity type and your role. This is where reporting a partnership K-1 and an S-corporation K-1 diverge sharply.

If you’re a general partner or an active member of a non-corporate LLC, your Box 1 income is generally subject to SE tax at 15.3%: 12.4% Social Security and 2.9% Medicare.5Internal Revenue Service. Self-Employment Tax (Social Security and Medicare Taxes) The Social Security portion stops at the annual wage base, which is $184,500 for 2026.6Social Security Administration. Contribution and Benefit Base Medicare has no cap, and an additional 0.9% Medicare surtax applies once combined earnings exceed $200,000 ($250,000 for joint filers).

Limited partners generally do not owe SE tax on Box 1. Any Box 4 guaranteed payments for services remain subject to SE tax.4Internal Revenue Service. Partners Instructions for Schedule K-1 (Form 1065)

S-corporation Box 1 income is not subject to SE tax at all. The trade-off is that a shareholder who performs substantial services must first take reasonable W-2 wages, on which Social Security and Medicare taxes are already withheld.7Internal Revenue Service. S Corporation Employees, Shareholders and Corporate Officers The Box 1 pass-through is what’s left after those wages, and it escapes the SE layer. This is the payroll-tax advantage of the S-corporation form, and it’s also the reason the IRS pays close attention to whether shareholder-employees are paying themselves realistically.

The QBI Deduction Starts With Box 1

The Section 199A Qualified Business Income deduction lets eligible owners deduct up to 20% of qualified business income. Legislation signed in July 2025 made the deduction permanent, so it continues to apply for 2026 and later years.

Your Box 1 figure is the starting point, but it isn’t QBI as-is. Partners subtract any guaranteed payments for services, because those don’t count as QBI even though they’re taxable. S-corporation shareholders subtract the W-2 wages the entity paid them.8Internal Revenue Service. Calculation of Plan Compensation for Partnerships

At lower taxable income levels the deduction is simply 20% of QBI. Above the threshold, limitations phase in based on the entity’s W-2 wages and depreciable property. For 2026 those thresholds are approximately $201,750 for most filers and $403,500 for joint filers, with the full phase-in complete around $276,750 and $553,500. Specified service businesses (health, law, accounting, consulting, athletics, financial services) lose the deduction entirely once income exceeds the upper threshold.

Reporting a Loss: Four Hurdles in Order

If Box 1 is negative, you can’t just drop the loss on Schedule E and move on. Four limitations apply in sequence, and each one must be cleared before the next matters.9Internal Revenue Service. S Corporation Stock and Debt Basis

1. Basis

You can only deduct a loss up to your adjusted basis in the entity. The definition of basis differs by entity type, and this is where owners most often go wrong.

A partner’s basis includes contributed cash and property plus a share of partnership liabilities, including certain nonrecourse debt. That liability inclusion is unique to partnerships and can create meaningful basis without any additional cash contribution.

An S-corporation shareholder’s basis is stock (from purchases and contributions) plus direct loans the shareholder personally makes to the corporation.10Office of the Law Revision Counsel. 26 U.S. Code 1366 – Pass-Thru of Items to Shareholders Corporate-level debt gives you no basis, even if you personally guarantee it. Only money you actually lend to the corporation counts. Shareholders regularly discover this the year they try to deduct a loss backed by a guaranteed bank loan.

Losses blocked at this step are suspended and carry forward indefinitely, releasing when you add basis through contributions (or, for partnerships, additional liabilities). S-corporation shareholders must file Form 7203 in any year they claim a loss, take a non-dividend distribution, dispose of stock, or receive a loan repayment from the corporation.11Internal Revenue Service. Instructions for Form 7203 One trap: if an S-corporation shareholder sells all their stock while losses remain suspended for lack of basis, those losses disappear permanently. They do not release on disposition the way passive losses do.9Internal Revenue Service. S Corporation Stock and Debt Basis

2. At-Risk

Losses that survive basis face the at-risk rules next. Your at-risk amount is generally what you contributed plus debt for which you’re personally liable. Nonrecourse financing, where you have no personal repayment obligation, is excluded. For most small businesses the at-risk amount roughly matches basis; the gap widens when the entity carries significant nonrecourse debt. Losses blocked here carry forward until you increase at-risk through additional contributions or by taking on personal liability.

3. Passive Activity

A loss that clears basis and at-risk still has to be classified as active or passive. If you don’t materially participate in the business, the loss is passive and can only offset income from other passive activities.12Internal Revenue Service. Publication 925 (2025), Passive Activity and At-Risk Rules It cannot offset wages, portfolio income, or non-passive business income.

The IRS lists seven tests for material participation. The most commonly used are the 500-hour test (more than 500 hours in the activity during the year) and the “substantially all” test (your participation is substantially all the participation by anyone, including non-owners). Other tests cover situations with more than 100 hours where no one else did more, and material participation in five of the last ten years. Meeting any one test is enough.12Internal Revenue Service. Publication 925 (2025), Passive Activity and At-Risk Rules

Suspended passive losses carry forward indefinitely and are fully released when you dispose of your entire interest in the activity in a fully taxable transaction with an unrelated party.13Office of the Law Revision Counsel. 26 U.S. Code 469 – Passive Activity Losses and Credits Limited On release, they become non-passive and can offset any income. Sales to related parties don’t trigger the release.

4. Excess Business Loss

The final hurdle caps total business losses across all your activities. If aggregate business losses exceed aggregate business income by more than a threshold amount, the excess is disallowed for the year and converts to a net operating loss carried forward. The threshold is inflation-adjusted and published in the Form 461 instructions.14Internal Revenue Service. Instructions for Form 461 For 2025 it was $313,000 for single filers and $626,000 for joint filers; the 2026 amount may differ following recent legislation.

If Your K-1 Is Wrong

Don’t fix a bad K-1 on your own return. Contact the entity’s preparer and push for a corrected K-1, which requires the entity to file an amended return. For partnerships not subject to the centralized audit rules, that means re-filing Form 1065 with the amended-return box checked, attaching corrected K-1s, and including a statement identifying what changed.15Internal Revenue Service. Guidance for Amended Partnership Returns Once you have the corrected K-1, amend your personal return on Form 1040-X. Waiting for the AUR system to catch the mismatch is the slower path; a CP2000 notice takes longer to resolve than a proactive amendment.

Track Your Basis Every Year

The IRS does not maintain your basis for you. The K-1 reports what happened during the year, but the running total is your job. Owners often ignore this until a loss year or a sale, then have to reconstruct records going back years.

S-corporation shareholders have Form 7203 for this purpose, required in any year of a loss, a distribution that could exceed stock basis, a stock disposition, or a loan repayment from the corporation.11Internal Revenue Service. Instructions for Form 7203 Completing it every year, even when not required, keeps your records straight. Partners have no equivalent mandatory form, but a similar year-by-year worksheet is worth keeping, particularly given how partnership liabilities complicate the calculation.

An understated basis can cause you to report phantom gain on a distribution or sale. An overstated basis lets you deduct losses you weren’t entitled to, and if the IRS catches it later, an accuracy penalty comes with the correction.