How Does a Schedule K-1 Affect Your Personal Taxes?

A Schedule K-1 tells you your share of a partnership, S corporation, or trust’s income, deductions, and credits for the year, and those numbers land directly on your personal tax return. Because the entity itself generally pays no income tax, the tax bill is yours. Depending on what the K-1 reports and how you participate in the business, it can drive regular income tax, self-employment tax, the 3.8 percent net investment income tax, the additional Medicare tax, and quarterly estimated payments. It can also do all of that in a year the business sent you no cash.

You Owe Tax Even If You Got No Cash

Partnerships, S corporations, and most trusts are pass-through entities: their income passes through to the owners rather than being taxed at the business level. Federal law states that a partnership itself is not subject to income tax, only the individual partners on their shares of the profits.¹ A similar rule applies to S corporations, which avoid the corporate-level tax that standard C corporations pay.² The entity files its own information return (Form 1065 for partnerships, Form 1120-S for S corporations) and sends each owner a K-1 showing that owner’s slice of the year.³

Here is where many new K-1 recipients get caught. Your share of the profits is taxable whether or not the business distributed anything to you. If the company reinvested everything or used the cash to pay down debt, you still owe the tax. That mismatch between a tax bill and an empty bank deposit is the single most common surprise on a first K-1.

No Withholding, So Plan for Quarterly Payments

K-1 income comes with no tax withheld at the source. You send the IRS money throughout the year using Form 1040-ES. For the 2026 tax year, the four due dates are April 15, June 15, September 15, and January 15, 2027.⁴

To avoid an underpayment penalty, your total payments (including any wage withholding from other jobs) must hit one of two safe harbors: at least 90 percent of your 2026 tax, or 100 percent of the tax shown on your 2025 return. If your 2025 adjusted gross income was above $150,000 ($75,000 if married filing separately), the prior-year safe harbor rises to 110 percent.⁵ Because K-1 income can swing year to year, many owners aim at the prior-year number so they have a fixed target.

How Each Box Is Taxed

The K-1 sorts your share of the entity’s results into numbered boxes, and each box controls the tax treatment on your return.

Box 1, ordinary business income or loss, is your share of day-to-day operating profit or loss.
Box 2, net rental real estate income or loss, is generally treated as passive.
Boxes 5 and 6, interest and dividends, are portfolio income and are not subject to the passive activity rules.
Box 9a, net long-term capital gains, keeps its favorable long-term rate on your return.
Box 13, other deductions, includes items like charitable contributions that you claim on your own Schedule A.³

The principle behind the boxes is that income keeps its character as it passes from the entity to you. A long-term capital gain earned inside the partnership stays a long-term capital gain on your 1040. A charitable contribution made by the entity flows through as a charitable contribution you can deduct if you itemize. Different categories face different rates and different limitation rules, so the character of the income matters as much as the dollar amount.

The 20 Percent Qualified Business Income Deduction

One of the biggest breaks for K-1 recipients is the qualified business income (QBI) deduction under Section 199A. If you qualify, you can deduct up to 20 percent of your share of ordinary business income from a pass-through entity, and you get the deduction without itemizing.⁶

The math is simple if your taxable income sits below roughly $200,000 (single) or $400,000 (joint) for 2026. Above those thresholds, limitations tied to the business’s W-2 wages and qualified property phase in. The deduction phases out entirely over a range of $75,000 above the threshold for single filers and $150,000 for joint filers.⁶

The rules tighten if the entity operates in a “specified service” field: health care, law, accounting, consulting, financial services, performing arts, or athletics, among others.⁷ Under the threshold, the service-business restriction does not apply and you still take the full deduction. Inside the phase-out range, the deduction for a specified service business shrinks quickly and disappears at the top of the range.

Self-Employment Tax Depends on Your Role

If you are a general partner, the ordinary business income on your K-1 is self-employment income, so Social Security and Medicare taxes stack on top of your regular income tax.⁸ The combined self-employment rate is 15.3 percent: 12.4 percent for Social Security and 2.9 percent for Medicare.⁹ The Social Security portion applies only to earnings up to $184,500 in 2026; the Medicare portion has no cap.¹⁰ You can deduct half of the self-employment tax when calculating adjusted gross income.

Limited partners and S corporation shareholders are treated differently. A limited partner’s share of ordinary income is generally excluded from self-employment tax, except for guaranteed payments received for services performed for the partnership.⁸ S corporation shareholders who work in the business take a salary that is already subject to payroll taxes; the remaining K-1 income flowing through as a distribution is not subject to self-employment tax. The IRS requires that salary to be reasonable based on the shareholder’s duties, experience, time devoted, and what comparable businesses pay for similar work.¹¹ Setting the salary too low to dodge payroll taxes is a well-known audit trigger.

Two Surtaxes That Catch Higher Earners

Additional Medicare Tax

If your combined self-employment income exceeds $200,000 ($250,000 for joint filers), the excess is hit with an additional 0.9 percent Medicare tax.¹² That sits on top of the 2.9 percent Medicare portion of self-employment tax, so a high-earning general partner faces an effective Medicare rate of 3.8 percent above the threshold.

Net Investment Income Tax

If your modified adjusted gross income exceeds $200,000 ($250,000 for joint filers), you may owe a 3.8 percent net investment income tax on certain K-1 income.¹³ The NIIT hits income from a business activity that is passive to you, meaning you do not materially participate in day-to-day operations.¹⁴ It also reaches interest, dividends, capital gains, and rental income reported on your K-1. The tax is calculated on the lesser of your net investment income or the amount your modified AGI exceeds the threshold.

Income from a business you actively participate in is generally exempt from the NIIT, and so are wages. The practical result: K-1 income that triggers self-employment tax for a general partner typically escapes the NIIT, while passive K-1 income that avoids self-employment tax often gets caught by the NIIT instead.

When Your K-1 Shows a Loss

A loss on your K-1 does not automatically reduce your taxable income. It has to pass three filters, in order, before it becomes deductible.¹⁵

First, basis. Your deductible share of a partnership loss cannot exceed your adjusted basis in the partnership, roughly what you have invested plus profits previously allocated to you, minus prior distributions and losses.¹⁶ For S corporation shareholders, the ceiling is the combined basis in your stock and any money you have personally loaned to the corporation. Blocked losses are not gone; they carry forward indefinitely and become deductible when your basis rises.¹⁷ S corporation shareholders track stock and debt basis on Form 7203, which is filed whenever you claim a loss deduction, receive a non-dividend distribution, or dispose of shares.¹⁸

Second, at-risk. You are at risk for money you contributed and for borrowed amounts you are personally liable to repay. Amounts protected by nonrecourse financing, guarantees, or stop-loss agreements do not count.¹⁹ Losses blocked here carry forward to a year when your at-risk amount is large enough.

Third, passive activity. If you did not materially participate in the business, a net loss can only offset other passive income. It cannot reduce wages, interest, or active business income.²⁰ Unused passive losses carry forward and can be used against later passive income, or when you dispose of your entire interest in the activity.¹⁵

Rental real estate has one useful exception. If you actively participated in managing a rental property, for example approving tenants and setting rental terms, you can deduct up to $25,000 of rental losses against non-passive income. The $25,000 allowance begins phasing out when your modified adjusted gross income exceeds $100,000 and disappears entirely at $150,000.¹⁵

Late K-1s and Filing Extensions

Calendar-year partnerships and S corporations must file their returns and issue K-1s to owners by March 15.²¹ If the entity files an extension, K-1s can arrive as late as September 15. Your personal return is due April 15, so a late K-1 often forces you to file your own extension.

Form 4868 gives you an automatic extension until October 15 to file your personal return. It extends only the filing deadline, not the payment deadline. You still have to estimate what you owe and pay by April 15 to avoid interest and late-payment penalties.²² If you receive K-1s from several entities, the slowest one sets your timeline.

Where the Numbers Go on Your Return

K-1 income from partnerships, S corporations, estates, and trusts is reported on Schedule E (Supplemental Income and Loss), which you attach to Form 1040.²³ Part II of Schedule E is where you enter the entity’s name, employer identification number, and the income or loss amounts from your K-1. The net total from Schedule E carries to Schedule 1 of Form 1040 and combines with your other income.²⁴

Some items go elsewhere. Interest income from Box 5 appears on Form 1040, capital gains from Box 9a on Schedule D, and charitable contributions from Box 13 on Schedule A if you itemize.³ Self-employment tax on partnership income is calculated on Schedule SE and reported on Schedule 2.

You do not file the K-1 itself; the entity already sends a copy to the IRS.³ Keep it with your records, and make sure the entity’s name and employer identification number on your return match the K-1 exactly. A mismatch can trigger processing delays or IRS notices.

1
Office of the Law Revision Counsel. 26 USC 701 – Partners, Not Partnership, Subject to Tax
2
Office of the Law Revision Counsel. 26 USC 1363 – Effect of Election on Corporation
3
Internal Revenue Service. Partners Instructions for Schedule K-1 (Form 1065) (2025)
4
Taxpayer Advocate Service. Making Estimated Tax Payments
5
Internal Revenue Service. Form 1040-ES – Estimated Tax for Individuals (2026)
6
Office of the Law Revision Counsel. 26 US Code 199A – Qualified Business Income
7
eCFR. 26 CFR 1.199A-5 – Specified Service Trades or Businesses and the Trade or Business of Performing Services as an Employee
8
Office of the Law Revision Counsel. 26 USC 1402 – Definitions
9
Internal Revenue Service. Self-Employment Tax (Social Security and Medicare Taxes)
10
Social Security Administration. Contribution and Benefit Base
11
Internal Revenue Service. S Corporation Compensation and Medical Insurance Issues
12
Internal Revenue Service. Topic No. 560, Additional Medicare Tax
13
Internal Revenue Service. Topic No. 559, Net Investment Income Tax
14
Office of the Law Revision Counsel. 26 US Code 1411 – Imposition of Tax
15
Internal Revenue Service. Publication 925, Passive Activity and At-Risk Rules
16
Office of the Law Revision Counsel. 26 USC 704 – Partners Distributive Share
17
Office of the Law Revision Counsel. 26 USC 1366 – Pass-Thru of Items to Shareholders
18
Internal Revenue Service. Instructions for Form 7203
19
Office of the Law Revision Counsel. 26 US Code 465 – Deductions Limited to Amount at Risk
20
Office of the Law Revision Counsel. 26 USC 469 – Passive Activity Losses and Credits Limited
21
Internal Revenue Service. Publication 509, Tax Calendars
22
Internal Revenue Service. Get an Extension to File Your Tax Return
23
Internal Revenue Service. About Schedule E (Form 1040), Supplemental Income and Loss
24
Internal Revenue Service. Schedule E (Form 1040) – Supplemental Income and Loss