What Is a K-1 Form for Taxes: Boxes, Filing, and Loss Limits

A K-1 form for taxes is a federal information return that reports your share of income, deductions, and credits from a partnership, S corporation, trust, or estate. You do not file the K-1 itself with your personal return, but you must carry its numbers onto your Form 1040 and the schedules that go with it. The catch worth understanding up front: because these entities are pass-through, you owe tax on your share of the entity’s income even if you received no cash distribution during the year.1Internal Revenue Service. Partner’s Instructions for Schedule K-1 (Form 1065)

Who Sends You a K-1

Three kinds of entities issue K-1s, and the version you receive depends on which one you have an interest in.

A partnership files Form 1065 and issues a K-1 to each partner reflecting that partner’s share of business income, losses, deductions, and credits, allocated according to the partnership agreement.2Internal Revenue Service. Instructions for Form 1065 (2025)1Internal Revenue Service. Partner’s Instructions for Schedule K-1 (Form 1065) An S corporation files Form 1120-S and sends a K-1 to every shareholder who held stock at any point during the year, with amounts allocated by ownership percentage.3Internal Revenue Service. Instructions for Form 1120-S, U.S. Income Tax Return for an S Corporation A trust or estate files Form 1041 and delivers a K-1 to each beneficiary who received a distribution of income.4Internal Revenue Service. About Form 1041, U.S. Income Tax Return for Estates and Trusts

A multi-member LLC is classified as a partnership by default unless it files Form 8832 to elect corporate treatment, so most LLC members receive a partnership-style K-1 from a Form 1065.5Internal Revenue Service. LLC Filing as a Corporation or Partnership Single-member LLCs are disregarded for federal tax purposes and do not issue K-1s.

What the Form Shows

Every K-1 has three parts. Part I identifies the entity by name, address, and employer identification number. Part II identifies you by name, taxpayer identification number, and your ownership percentage or share of liabilities. Part III lists the dollar amounts allocated to you.

Common line items in Part III include:

  • Ordinary business income or loss — the entity’s operating result
  • Net rental real estate income or loss
  • Interest and dividends, listed separately because they can be taxed at different rates
  • Capital gains and losses, split between short-term and long-term
  • Self-employment earnings, in Box 14 of a partnership K-1

Coded Boxes

Some boxes use letter codes for less common items. Box 20 on a partnership K-1 and Box 17 on an S corporation K-1 use codes that map to detailed explanations in the IRS instructions, and you have to look each one up to know whether it produces a deduction, a credit, or an adjustment.1Internal Revenue Service. Partner’s Instructions for Schedule K-1 (Form 1065)

Qualified Business Income

One code worth watching is Box 20, Code Z on a partnership K-1, which carries the data supporting the qualified business income deduction. That provision lets eligible taxpayers deduct up to 20% of net qualified business income from a pass-through entity, calculated on Form 8995 or Form 8995-A depending on income level.1Internal Revenue Service. Partner’s Instructions for Schedule K-1 (Form 1065) For 2026, the simplified Form 8995 calculation generally applies when taxable income before the deduction is roughly $200,000 or less, or $400,000 or less for joint filers; above those thresholds the deduction can be limited or phased out depending on the type of business.

Where Each Number Goes on Your Return

The amounts on your K-1 do not land in one place on Form 1040. They fan out across several schedules:

Tax software will normally route each entry automatically once you enter the boxes as they appear. If you prepare by hand, the partner’s or beneficiary’s instructions accompanying the K-1 give a line-by-line map to the correct destination.

Self-Employment Tax

General partners and members of an LLC taxed as a partnership generally owe self-employment tax on their share of ordinary business income, covering the Social Security and Medicare portions that self-employed individuals pay in place of payroll withholding.7Internal Revenue Service. Entities 1

Limited partners owe self-employment tax only on guaranteed payments for services, not on their regular profit share.7Internal Revenue Service. Entities 1 S corporation shareholders do not owe self-employment tax on their K-1 income at all, but the corporation must pay them a reasonable salary for services performed, and that salary is subject to standard payroll taxes.

A Loss on Your K-1 May Not Be Deductible Yet

Three limitation rules apply in sequence when your K-1 shows a loss. You have to clear all three before the loss reduces your taxable income.

Basis

You can deduct losses only up to your adjusted basis in the entity. Basis generally starts with your capital contribution and moves up with additional contributions and your share of income, and down with distributions and losses. Any loss beyond basis carries forward until you rebuild enough basis to use it.8Internal Revenue Service. New Limits on Partners’ Shares of Partnership Losses Frequently Asked Questions

At-Risk

Losses are then limited to the amount you have at risk in the activity, meaning money you could actually lose. Nonrecourse debt (where you are not personally liable) generally does not count as at risk, with a carve-out for certain real estate financing. Form 6198 handles the calculation.9Internal Revenue Service. Instructions for Form 6198

Passive Activity

If you did not materially participate in the business on a regular, continuous, and substantial basis, the loss is passive and can only offset other passive income, not wages or portfolio income. Rental real estate has a special rule: if you actively participated in managing the property and your modified adjusted gross income is $100,000 or less, you can deduct up to $25,000 of passive rental losses against non-passive income. The allowance phases out between $100,000 and $150,000 of modified AGI and disappears above $150,000. Unused passive losses carry forward until you have passive income to absorb them or you dispose of your entire interest in the activity.10Internal Revenue Service. Instructions for Form 8582 – Passive Activity Loss Limitations

Deadlines and Late K-1s

Partnerships and S corporations must file their returns and furnish K-1s by the 15th day of the third month after their tax year ends. For calendar-year entities, that is March 15 (or March 16 when the 15th falls on a weekend).11Internal Revenue Service. Publication 509 (2026), Tax Calendars Your personal return is due April 15, which leaves a tight month to fold the K-1 into your own filing.

The entity can file Form 7004 for an automatic six-month extension (five and a half months for trusts and estates), pushing a calendar-year partnership’s K-1 delivery out to September 15.12Internal Revenue Service. Instructions for Form 7004 If you are waiting on a delayed K-1, filing Form 4868 extends your own individual return to October 15 and avoids the late-filing penalty.13Internal Revenue Service. Get an Extension to File Your Tax Return The extension is only for filing, not paying; tax owed is still due April 15, and interest runs from that date on any balance.14Internal Revenue Service. Form 4868 Application for Automatic Extension of Time To File U.S. Individual Income Tax Return

If a K-1 lands after you have already filed, file Form 1040-X to amend the return and add the missing items.15Internal Revenue Service. Instructions for Form 1040-X (Rev. September 2024) Leaving K-1 income off your return can trigger an IRS notice plus interest on any underpayment.

When Your K-1 Is Wrong

Contact the partnership, S corporation, or trust representative and ask for a corrected form. If the entity will not fix it, file your own return using the figures you believe are correct and attach Form 8082 to notify the IRS that your return does not match the K-1 you received. Filing an inconsistent return without Form 8082 can lead to automatic adjustments, penalties, and interest.

Estimated Tax Payments

Pass-through entities do not withhold federal income tax the way employers do, so you may need to make quarterly estimated payments to avoid an underpayment penalty. The IRS generally requires estimated tax if you expect to owe $1,000 or more after withholding and refundable credits.16Internal Revenue Service. Estimated Taxes You can typically avoid the penalty by paying at least 90% of the current year’s tax or 100% of the prior year’s tax (110% if your prior-year adjusted gross income exceeded $150,000).17Internal Revenue Service. Estimated Tax Payments use Form 1040-ES, with due dates in April, June, September, and January.

State and Foreign Situations

If the entity operates in a state other than where you live, you may owe income tax to that state on the income earned there. Many states require partnerships to withhold on behalf of nonresident partners; you would then file a nonresident return in that state and generally claim a credit on your home-state return for the taxes paid.

If the entity has foreign-source income or pays foreign taxes, you may also receive a Schedule K-3 alongside the K-1, providing the country-by-country detail you need to claim a foreign tax credit on Form 1116.18Internal Revenue Service. Partner’s Instructions for Schedule K-3 (Form 1065) (2025) Separately, an interest in a foreign partnership or specified foreign financial assets above certain thresholds can trigger a Form 8938 reporting requirement.19Internal Revenue Service. Do I Need to File Form 8938, Statement of Specified Foreign Financial Assets

Recordkeeping

The IRS generally expects you to keep records supporting your return for at least three years from the filing date.20Internal Revenue Service. How Long Should I Keep Records For a partnership or S corporation interest, keep every K-1 for as long as you hold the interest, plus three years after you dispose of it. The running basis those forms document will decide how much loss you can deduct along the way and how much gain you report when you finally sell.