K-1 Income Tax Rate: How to Estimate the Tax on Your K-1

By Kevin Luu, Co-Founder and Chief Learning Officer. Reviewed on 2026-09-30.

There is no single K-1 income tax rate. Each line of your Schedule K-1 is taxed at the rate that applies to that type of income on your own return, so the fastest way to estimate it is to multiply each type by your marginal rate for that type. For a California family with joint taxable income over $1.5 million, that typically means about 54% on ordinary K-1 income and about 37% on long-term capital gains for 2026 (federal plus the 3.8% Net Investment Income Tax plus California’s 13.3% top rate from its 2025 schedule, the latest published); in Washington it is about 41% and 24%, as long as the family’s gains stay under Washington’s capital gains deduction.

This page shows the five-step method we use to estimate the tax on a K-1 before it arrives, a worked example for a two-income household, and how to cover the bill so it does not turn into a penalty. For a box-by-box table of how each K-1 line is taxed, see our companion guide, K-1 tax rate: how K-1 income is taxed for high-earning families.

Why a K-1 has no rate of its own

A partnership or S corporation usually pays no federal income tax itself, and a trust or estate generally pays tax only on the income it keeps. Each passes its income, gains, deductions and credits through to the owners on a Schedule K-1, and each owner reports their share on Form 1040. The IRS instructions state that a partner may be liable for tax on their share of partnership income “whether or not distributed” (Partner’s Instructions for Schedule K-1, Form 1065).

So the rate depends on two things: what kind of income the K-1 reports, and where your other income already puts you. For a household earning $750,000 to $3 million in W-2 pay and RSU vests, K-1 income is stacked on top of the salary. It is taxed at your highest brackets, not at an average rate.

Which K-1 you have: 1065, 1120-S or 1041

The three versions of the form come from different entities, and the queries people search (“1065 K-1 instructions”, “1120-S K-1 instructions”, “1041 K-1”) reflect that. For W-2 families they usually mean:

• Form 1065 K-1 (partnership or LLC). Private equity, venture and real estate funds, syndications, publicly traded partnerships, and a spouse’s medical or professional partnership. The most common K-1 in this group.
• Form 1120-S K-1 (S corporation). Less common for W-2 families; usually an investment in a friend’s or relative’s company, or a side business owned with a spouse.
• Form 1041 K-1 (trust or estate). Income a trust or estate distributes to beneficiaries, for example from a parent’s estate being settled or a family trust. The trust or estate takes a deduction for the income it distributes, which then becomes taxable to the beneficiaries, and it generally pays tax itself on what it keeps (Instructions for Form 1041).

The estimating method below works the same way for all three. Only the box numbers change, and the form’s own instructions tell you where each amount goes on your return. Our guide to where K-1 income goes on the 1040 walks through that part.

A five-step K-1 income tax calculator you can do on paper

Many online K-1 calculators apply one average rate to the whole K-1, which understates the tax for this income level. This method is closer to what your CPA will compute.

1. Find your federal marginal bracket without the K-1. For 2026, joint filers pay 35% on taxable income from $512,450 to $768,700 and 37% above $768,700 (IRS Rev. Proc. 2025-32). Most households in the $750,000 to $3 million range are in one of these two.
2. Sort the K-1 into two buckets. Ordinary: business income, interest, ordinary dividends, short-term gains, fixed payments a partnership makes to a working partner. Preferential: qualified dividends and long-term capital gains, taxed at 20% for 2026 once joint taxable income passes $613,700 (same source). Some real estate gain (unrecaptured section 1250 gain) is taxed at up to 25% (IRS Topic 409).
3. Add 3.8% for the Net Investment Income Tax. It applies to investment income and to business income that is passive to you, once modified AGI passes $250,000 for joint filers (IRS NIIT page). If you are a fund investor, assume it applies.
4. Add state tax. California taxes every type at ordinary rates because it has no lower capital gains rate (FTB). Its top rate is 13.3%: 12.3% on joint taxable income over $1,485,906 plus the 1% Behavioral Health Services Tax on taxable income over $1,000,000 (2025 schedule, the latest published; FTB 2025 rate schedules). Washington has no wage income tax in 2026 and taxes long-term capital gains at 7% only above an annual deduction ($278,000 for 2025, the latest published by the Department of Revenue).
5. Multiply, then compare with the cash. Multiply each bucket by its combined rate, add them up, and set that figure beside the cash the fund actually distributed. The gap is what you fund from savings.

Worked example: a $1.6 million Palo Alto household with three K-1s

Assumptions (illustrative): married filing jointly, two children aged 4 and 8. One spouse is an Apple engineer with RSUs, the other a hospital-employed physician. Combined W-2 income is about $1.6 million, and both federal and California taxable income are above $1.5 million before any K-1. They hold a private equity fund, a real estate debt fund and a small inherited share of a grandparent’s estate that is still being settled. All three are passive investments.

Their K-1s for the year show $66,000 of income: $40,000 of long-term capital gains and $8,000 of ordinary business income from the private equity fund, $12,000 of interest from the debt fund, and $6,000 of interest on a Form 1041 K-1 from the estate. The funds distributed $25,000 in cash.

The Washington column assumes the same family lived in Bellevue and that their total long-term gains for the year stayed under the Washington deduction, so no state capital gains tax applies. If their gains from all sources exceeded it, the excess would be taxed at 7%, rising to 9.9% on the part of taxable gains above $1 million (Washington DOR).

Three takeaways. The tax ($28,906 in California) is higher than the cash received ($25,000), so the K-1 costs them money out of pocket this year. The “rate” is really two rates, 54.1% and 37.1%, and the mix of income decides the blend. And the move from California to Washington changes the answer more than anything the funds do. For completeness: Washington has enacted a 9.9% income tax on AGI over $1,000,000 starting in 2028 (Washington DOR), so this gap narrows for high earners from then.

Two refinements your CPA may apply. Box 1 business income can qualify for the qualified business income deduction (IRS QBI page), which would lower the federal figure somewhat; treat it as a possible reduction rather than part of the estimate. And a K-1 loss does not simply subtract from the table: passive losses generally only offset passive income, not wages (IRS Publication 925).

How to pay K-1 tax without an underpayment penalty

Nothing is usually withheld on K-1 income, and RSU withholding often already falls short: employers typically withhold 22% federal on supplemental wages up to $1 million for 2026, while this family’s marginal rate is 37% (IRS Publication 15). Adding K-1 income widens the gap.

To avoid the underpayment penalty, the IRS generally expects you to pay, through withholding and estimated payments, at least 90% of this year’s tax or 100% of last year’s tax (IRS estimated taxes). If last year’s AGI was over $150,000 ($75,000 married filing separately), the prior-year figure becomes 110% (Form 2210 instructions). Families in our reader range are almost always in the 110% group.

In practice, the federal prior-year safe harbor is the simplest route when K-1 income is hard to predict: once last year’s return is filed you know the figure, so you can set withholding or quarterly payments to hit 110% of it and settle the rest when you file. California is stricter for this family: if your California AGI for the current year is $1,000,000 or more ($500,000 married filing separately), the prior-year option is not available and estimated payments must be based on 90% of the current year’s tax (FTB estimated tax payments). A California household above that line has to estimate the K-1 income itself, which is one more reason to run the five steps early. K-1s are due to partners by the partnership’s return due date, March 15 for calendar-year partnerships, and later if the partnership extends (Form 1065 instructions). That is why families with fund K-1s often extend their own return with Form 4868. An extension gives more time to file, not to pay. More on timing in when you should receive your K-1.

Common mistakes when estimating K-1 tax

• Using your average tax rate. K-1 income sits on top of your wages, so your marginal rate is the one that matters.
• Budgeting from the distribution. Tax follows the allocated income, not the cash. Some years the fund sends nothing and you still owe.
• Forgetting the 3.8%. At this income level it applies to almost all passive K-1 income.
• Assuming capital gains are cheap in California. They are taxed at the same state rate as salary.
• Treating K-1 income as earned income. Passive K-1 income generally does not count as earned income for things like IRA contributions or a child’s custodial Roth. See does K-1 income count as earned income.

The decision behind the estimate

The estimate is not the real question. The real question is whether a private fund still earns its place in the portfolio once you account for a 54% tax rate on its ordinary income, a late form every spring, and cash held back for the bill. For some families the answer is yes. For others, the same exposure in a tax-efficient public fund is simpler and keeps more after tax. Our investment and risk management work looks at that trade-off fund by fund.

What to write down for your kids

Private funds often run ten years or more, which means your children may be the ones receiving the K-1s. Keep a one-page note for each fund in your FamilyKnowledge® Library: why you invested, what you expected it to return after tax, when its K-1 usually arrives, and who prepares the return. Conversations fade. Documentation compounds.

FAQ

Do I owe tax on K-1 income if I received no distribution?

Yes, generally. You are taxed on your allocated share of the entity’s income for the year, whether or not it paid out cash. Distributions themselves are usually not taxed again unless the cash exceeds your adjusted basis in the investment. That is why a profitable fund that reinvests its earnings can leave you with a tax bill and no cash to pay it from.

Is K-1 income taxed higher than W-2 income?

Ordinary K-1 income is taxed at the same federal brackets as wages. Passive K-1 income skips Social Security and Medicare payroll tax but usually picks up the 3.8% Net Investment Income Tax instead. K-1 income from a business you actively work in, such as a medical partnership, can instead be subject to self-employment tax. Long-term gains on a K-1 get the lower federal capital gains rates.

Is there a reliable K-1 income tax calculator?

Many free calculators apply one rate to the whole K-1, which understates the tax for high earners. The five-step method above, using your marginal federal bracket, the capital gains rate, the 3.8% tax and your state rate, gets you within a reasonable range. Your CPA’s projection, run with the actual K-1 boxes, is the figure to budget from.

Next step

List every K-1 you expect for this year, sort last year’s amounts into the two buckets, and run the five steps. If the total is larger than the cash you expect, raise your withholding or schedule an estimated payment now rather than in April. If you would like us to run it with you as part of a Tax & Wealth Assessment, start with our tax management page.

This is general education, and the right move depends on your family’s full picture.

Written by

Kevin Luu

Co-Founder and Chief Learning Officer, Bright Advisers

Kevin has advised high-income W-2 tech and biotech families since 2015, and leads the education-first Age Five Family Office from Brea, California.

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