Excise Tax on Private Foundations: 2026 Guide

Excise Tax on Private Foundations: 2026 Guide

Excise Tax on Private Foundations: 2026 Complete Guide

The excise tax on private foundations is one of the most misunderstood areas of nonprofit tax law — and one of the costliest to get wrong. For the 2026 tax year, private foundations face a 1.39% tax on net investment income under IRC Section 4940, plus up to five additional penalty excise taxes if they violate key compliance rules. Whether you run a family foundation or advise one, understanding these rules is essential to protecting your assets, your mission, and your tax-exempt status. Our high-net-worth tax strategy team helps foundation leaders navigate these rules with confidence.

This information is current as of 5/24/2026. Tax laws change frequently. Verify updates with the IRS if reading this later.

Table of Contents

• Key Takeaways
• What Is a Private Foundation and Why Does It Face Excise Taxes?
• What Is the 1.39% Net Investment Income Tax on Private Foundations?
• What Are the Five Penalty Excise Taxes Private Foundations Must Avoid?
• What Is the 5% Minimum Distribution Requirement for 2026?
• How Can Private Foundations Avoid Costly Self-Dealing Violations?
• What Are the 2026 Filing Requirements for Private Foundations?
• Uncle Kam in Action: Protecting a Family Foundation from a Six-Figure Penalty
• Next Steps
• Related Resources
• Frequently Asked Questions

Key Takeaways

• For 2026, private foundations pay a 1.39% excise tax on net investment income under IRC Section 4940.
• Five additional penalty excise taxes apply under IRC Sections 4941–4945 for prohibited acts.
• Foundations must distribute at least 5% of net investment assets annually to avoid a 30% penalty tax.
• Self-dealing violations carry an initial 10% excise tax and a punishing 200% additional tax if uncorrected.
• Form 990-PF is the annual filing vehicle, and quarterly estimated payments are required when tax exceeds $500.

What Is a Private Foundation and Why Does It Face Excise Taxes?

A private foundation is a specific type of nonprofit organization recognized under IRS Section 501(c)(3). Unlike public charities, private foundations typically receive funding from a single individual, family, or corporation. This concentrated control creates unique risks of abuse — which is exactly why Congress enacted the excise tax on private foundations regime under IRC Chapter 42.

How the IRS Classifies Private Foundations

The IRS presumes that every 501(c)(3) organization is a private foundation. However, an organization can avoid this classification. It does so by demonstrating that it meets the requirements of a public charity. Public charities must receive broad public support or operate active programs. If they cannot prove this, they remain private foundations and face all related excise tax rules.

Furthermore, private foundations come in two main types. A “grant-making” foundation distributes funds to outside organizations. A “private operating foundation” runs its own charitable programs directly. Both types face the 1.39% excise tax on net investment income. However, private operating foundations are exempt from the mandatory 5% distribution requirement under IRC Section 4942.

Why Congress Created These Taxes

The Tax Reform Act of 1969 introduced the private foundation excise tax framework. Congress was concerned about wealthy donors using foundations to delay charitable giving, engage in self-serving transactions, and accumulate business interests. As a result, the law created several specific prohibitions. It also established penalty excise taxes to enforce these rules with real financial consequences.

Today, these rules remain largely unchanged in structure. However, some rates and thresholds have shifted over time. The 2026 net investment income tax rate of 1.39% reflects a simplification from the old two-tier system (1% or 2%) that Congress replaced in the Taxpayer Certainty and Disaster Tax Relief Act of 2019. This single flat rate makes planning much more predictable for foundation managers. If you want proactive tax planning for your foundation, working with a specialist is a smart first step.

What Is the 1.39% Net Investment Income Tax on Private Foundations?

The excise tax on private foundations’ net investment income is the most routine annual tax that foundation managers must handle. Under IRC Section 4940, the 2026 rate is 1.39%. This applies to most domestic private foundations. Foreign foundations face a 4% rate instead.

What Counts as Net Investment Income?

Net investment income (NII) includes several types of income. Specifically, it covers interest, dividends, rents, royalties, and net capital gains. It also includes income from activities that are not substantially related to the foundation’s charitable purpose. You subtract ordinary and necessary expenses directly connected to generating this income. However, you cannot deduct capital losses against capital gains from a prior year under the private foundation rules.

Therefore, a foundation with a $10 million investment portfolio generating $300,000 in dividends and $100,000 in capital gains would owe approximately $5,560 in excise tax for 2026 (1.39% × $400,000 = $5,560). This is a relatively modest tax compared to the penalties that flow from the five prohibited act excise taxes described below.

Estimated Tax Payment Requirements

If a private foundation expects its annual Section 4940 excise tax to be $500 or more, it must make quarterly estimated tax payments. For calendar-year foundations, the first deposit for 2026 was due by May 15, 2026. Subsequent payments are due August 15, November 15, and February 15. Payments must be made electronically through the Electronic Federal Tax Payment System (EFTPS).

Failure to make timely estimated payments results in interest and penalties. Moreover, the IRS may treat the underpayment as a signal for further examination. Consequently, most well-managed foundations set up automatic EFTPS payments early in the year.

What Are the Five Penalty Excise Taxes Private Foundations Must Avoid?

Beyond the routine net investment income tax, the excise tax on private foundations includes five separate penalty regimes. Each one targets a specific type of prohibited behavior. These taxes can be severe — in some cases reaching 200% of the amount involved. Together, they form the core compliance challenge for every private foundation in 2026.

IRC Section	Prohibited Act	Initial Tax	Additional Tax
4940	Net Investment Income	1.39% of NII	N/A
4941	Self-Dealing	10% (disqualified person); 5% (manager)	200% (disqualified person); 50% (manager)
4942	Failure to Distribute	30% of undistributed amount	100% if not corrected
4943	Excess Business Holdings	10% of excess holdings	200% if not corrected
4944	Jeopardizing Investments	10% on foundation; 10% on manager	25% if not removed
4945	Taxable Expenditures	20% on foundation; 5% on manager	100% on foundation if not corrected

IRC Section 4941: Self-Dealing

Self-dealing is the most dangerous and frequently triggered violation for family foundations. Under IRC Section 4941, a private foundation may not engage in certain transactions with “disqualified persons.” Disqualified persons include substantial contributors, foundation managers, owners of more than 20% of a business that is a substantial contributor, and family members of any of the above.

Prohibited self-dealing acts include the sale or lease of property, lending money, providing goods or services, paying excessive compensation, and transferring income or assets for the benefit of a disqualified person. The initial tax for 2026 is 10% of the amount involved, imposed on the disqualified person. A foundation manager who knowingly participated faces an additional 5% initial tax. If the act is not corrected within the taxable period, a 200% additional tax applies to the disqualified person. The manager faces 50% if they refuse to correct the violation.

There is a $20,000 cap on the initial tax for any one act against a foundation manager. However, there is no cap on the disqualified person’s liability. This asymmetry is intentional — Congress wanted to deter wealthy donors from exploiting their own foundations.

IRC Section 4943: Excess Business Holdings

Section 4943 limits how much of a business enterprise a private foundation (together with all disqualified persons) can own. In general, the foundation and all disqualified persons combined may not own more than 20% of the voting stock in a corporation. For businesses not traded on an exchange, the foundation may own no more than a 35% interest if a third party effectively controls the company. Violations carry a 10% initial excise tax and a severe 200% additional tax if the excess holdings are not disposed of within the correction period.

What Is the 5% Minimum Distribution Requirement for 2026?

The minimum distribution requirement (MDR) is one of the most operationally critical rules for grant-making foundations. Congress designed it to prevent foundations from indefinitely accumulating wealth without making charitable distributions. For 2026, the rule requires foundations to distribute an amount equal to at least 5% of the average fair market value of investment assets, minus the 1.39% net investment income tax paid.

Calculating Your 2026 Distributable Amount

The distributable amount calculation follows these steps:

• Step 1: Calculate the average monthly fair market value of all investment assets for 2026.
• Step 2: Multiply by 5% to get the minimum investment return.
• Step 3: Subtract taxes paid under Section 4940 (the 1.39% tax).
• Step 4: The result is your distributable amount for 2026.

For example, consider a foundation with average investment assets of $20 million in 2026. The minimum investment return is $1,000,000 (5% × $20M). If the foundation paid $40,000 in Section 4940 taxes, the distributable amount would be $960,000. The foundation must make qualifying distributions of at least $960,000 during 2026 to avoid the Section 4942 penalty excise tax.

What Counts as a Qualifying Distribution?

Not every expenditure counts as a qualifying distribution. The IRS specifically recognizes the following as qualifying:

• Grants to public charities and qualifying organizations.
• Reasonable and necessary administrative expenses to accomplish charitable purposes.
• Amounts paid to acquire program-related investments (PRIs).
• Amounts set aside for specific projects, subject to IRS approval.

However, grants to most non-operating private foundations do not count as qualifying distributions unless special safeguards are in place. Similarly, grants to individuals generally require prior IRS approval of the foundation’s selection procedures. Failing to follow these rules can create a double problem — the grant doesn’t count toward your MDR, and it may trigger a Section 4945 taxable expenditure penalty.

Consequences of Failing the 5% Requirement

The penalty for violating Section 4942 is steep. The IRS imposes an initial 30% excise tax on the undistributed amount. If the foundation still fails to correct the shortfall within the correction period, the IRS can impose a 100% additional tax. In extreme cases, repeated violations can jeopardize the foundation’s tax-exempt status altogether. Therefore, monitoring your minimum distribution requirement throughout the year — not just at year-end — is essential for 2026 compliance.

How Can Private Foundations Avoid Costly Self-Dealing Violations?

Self-dealing violations are particularly dangerous because they are strict-liability offenses. The tax applies even if the transaction was fair to the foundation and beneficial to the charitable mission. Consequently, good intentions are not a defense under IRC Section 4941. Prevention is the only reliable strategy.

Identify Every Disqualified Person First

The first step in avoiding self-dealing is building a comprehensive list of all disqualified persons connected to your foundation. This list typically includes the following people and entities:

• The original donor and substantial contributors (anyone who gave more than $5,000 if that amount also exceeds 2% of total contributions).
• Foundation managers, including trustees, directors, and officers.
• Family members (spouses, ancestors, descendants, spouses of descendants) of any substantial contributor or manager.
• Corporations, partnerships, trusts, and estates owned more than 35% by disqualified persons.

Many family foundation trustees are surprised to learn how broadly “disqualified person” is defined. For example, a foundation created by a parent may treat the children, their spouses, and even the grandchildren as disqualified persons. Therefore, a grant to an organization run by a grandchild could trigger a self-dealing violation unless carefully structured.

Common Self-Dealing Pitfalls to Watch in 2026

Several recurring transaction patterns trigger Section 4941 violations. Foundation managers should be vigilant about these specific scenarios in 2026:

• Renting office space from a disqualified person, even at fair market rates.
• Hiring a disqualified person’s business for goods or services without proper approvals.
• Paying above-market compensation to a disqualified person who serves as an employee.
• Lending foundation funds to a disqualified person, even with market interest rates.
• Using foundation assets to pay for personal expenses of a disqualified person, such as travel.

Note that some transactions are specifically exempt from the self-dealing rules. For instance, a disqualified person may receive reasonable compensation for services actually needed by the foundation. The IRS also allows certain indirect benefits that are incidental and tenuous. Nevertheless, these exceptions are narrow. Always get a legal opinion before proceeding with any transaction involving a disqualified person.

What Are the 2026 Filing Requirements for Private Foundations?

Private foundations face extensive annual reporting requirements. These filings are not optional — they are mandatory for maintaining tax-exempt status. Failure to file for three consecutive years results in automatic revocation of exemption under IRS rules. For 2026, the following filing obligations apply to nearly all domestic private foundations.

Form 990-PF: The Annual Foundation Return

Form 990-PF is the primary annual information return for private foundations. It captures the foundation’s financial activity, charitable distributions, investment income, excise tax calculations, and governance information. The form is due by the 15th day of the 5th month after the close of the tax year. For calendar-year foundations, that means May 15, 2026 for the 2025 tax year return, and May 15, 2027 for the 2026 tax year return.

Foundations can request a 6-month automatic extension using Form 8868. However, any tax owed must still be paid by the original due date to avoid interest and penalties. The Form 990-PF is publicly available, meaning anyone can request a copy. This transparency requirement is an important accountability mechanism that the IRS enforces strictly.

Form 4720: Reporting and Paying Penalty Excise Taxes

When a private foundation (or a disqualified person connected to it) has engaged in a prohibited transaction, they must file Form 4720. This form calculates the initial and additional excise taxes under IRC Sections 4941–4945. Both the foundation and the individual disqualified person may need to file their own separate Form 4720 returns. For expert assistance with foundation tax filings, Uncle Kam’s team handles both Form 990-PF and Form 4720 compliance.

Public Disclosure Obligations

Private foundations must make certain documents publicly available. These include the last three years of Form 990-PF returns and the original exemption application. Anyone who requests these documents in person must be able to inspect them immediately. Requests by mail must be fulfilled within 30 days. Foundations that post their returns on a publicly accessible website may satisfy this requirement without responding to individual requests.

2026 Filing Obligation	Form	Due Date (Calendar Year)	Extension Available
Annual Return	990-PF	May 15	Yes – 6 months (Form 8868)
Penalty Excise Taxes	4720	Same as 990-PF	Yes – 6 months
Quarterly Estimated Tax (if ≥$500)	EFTPS	May 15, Aug 15, Nov 15, Feb 15	No
Public Disclosure	990-PF (last 3 years)	Ongoing	N/A

 

 

Uncle Kam in Action: Protecting a Family Foundation from a Six-Figure Penalty

Client Snapshot: A Boston-based entrepreneur and his wife established a family private foundation in 2022 with an initial gift of $15 million. The foundation’s mission centered on education and arts funding in the greater Boston area. By early 2025, the foundation had grown to $22 million in assets due to strong investment returns. However, the founders had been managing the foundation largely on their own, relying on generic nonprofit software without specialized tax guidance.

The Challenge: When the family engaged Uncle Kam for a comprehensive review ahead of the 2026 tax year, our team quickly identified three serious compliance gaps. First, the foundation had underdistributed by approximately $120,000 in 2024 relative to its Section 4942 minimum distribution requirement. Second, the foundation had been paying rent to a property management company in which the founder held a 45% ownership interest — a clear self-dealing violation under IRC Section 4941. Third, the foundation had never established a conflict-of-interest policy, and the board had never formally documented its annual compliance review.

The Uncle Kam Solution: Our team moved immediately on three fronts. We calculated the exact underdistributed amount under Section 4942 and structured a plan to make corrective distributions before the taxable period expired, eliminating the 100% additional tax risk. Next, we documented the self-dealing property lease, quantified the amount involved, and prepared Form 4720 with a first-tier correction strategy to minimize the Section 4941 initial tax exposure. We also negotiated an immediate termination of the lease and helped the foundation find a third-party vendor, which stopped the accrual of additional violations. Finally, we created a written governance framework — including an annual compliance calendar, a conflict-of-interest policy, and a disqualified person registry — to prevent future violations.

The Results: By correcting the underdistribution within the taxable period, the family avoided the 100% additional Section 4942 tax, saving over $120,000 in potential penalties. The self-dealing correction reduced the Section 4941 exposure from what could have been a $140,000+ penalty to a manageable first-tier tax. The family invested approximately $18,000 in Uncle Kam’s advisory services and saved an estimated $260,000+ in combined excise taxes and penalties — a first-year ROI exceeding 14x. View more stories like this on our client results page.

Next Steps

Managing the excise tax on private foundations requires proactive planning throughout the year — not just at tax time. Here are five concrete actions to take now for 2026 compliance. Our private foundation tax advisory team is ready to help with every step.

• Calculate your 2026 distributable amount now and map out a grant schedule to meet the 5% minimum by year-end.
• Build and maintain a current list of all disqualified persons connected to your foundation.
• Review all vendor contracts and leases to identify any hidden self-dealing exposures before they compound.
• Confirm your quarterly Section 4940 estimated tax payments are set up through EFTPS if your annual tax will exceed $500.
• Schedule a year-end compliance review with a qualified tax advisor to confirm all filings are on track. You can also explore our Small Business Tax Calculator for Boston to model your foundation’s tax exposure for 2026.

Related Resources

• High-Net-Worth Tax Strategies at Uncle Kam
• Uncle Kam Tax Strategy Services
• Tax Preparation and Filing for Nonprofits
• Uncle Kam Tax Guides
• The MERNA Method for Strategic Tax Planning

Frequently Asked Questions

What is the excise tax rate on private foundation net investment income for 2026?

For 2026, the excise tax on private foundations’ net investment income under IRC Section 4940 is a flat 1.39%. This applies to most domestic private foundations. Foreign private foundations face a higher rate of 4%. The 1.39% rate replaced the old two-tier system in 2020 and has remained unchanged since. The tax is reported on Form 990-PF and must be paid annually. Quarterly estimated payments are required if the total tax is expected to be $500 or more.

Who counts as a disqualified person under private foundation self-dealing rules?

Disqualified persons include substantial contributors (individuals who gave more than $5,000 if that amount also exceeds 2% of total contributions), foundation managers (trustees, directors, officers), government officials, and certain family members. Family members of disqualified persons include spouses, ancestors, lineal descendants, and spouses of descendants. Corporations, partnerships, trusts, and estates owned more than 35% by disqualified persons are also disqualified. The definition is intentionally broad. Therefore, family foundations should maintain a current, written list of all disqualified persons and update it annually.

What happens if a private foundation does not meet the 5% distribution requirement?

If a private foundation fails to distribute the required 5% of net investment assets, the IRS imposes an excise tax of 30% on the undistributed amount under IRC Section 4942. This initial tax is automatic. If the foundation does not make corrective distributions within the taxable period (generally the year the tax was imposed plus 90 days), the IRS can impose an additional 100% tax on the remaining undistributed amount. In the most severe cases, chronic failure to distribute can lead to the termination of the foundation’s tax-exempt status. Private operating foundations are exempt from this rule, but all grant-making foundations must comply.

Can a private foundation pay its family members for work they do for the foundation?

Yes, but with important restrictions. Under IRC Section 4941, paying reasonable compensation to a disqualified person for personal services actually needed by the foundation is specifically excluded from the self-dealing prohibition. However, the compensation must be reasonable — meaning it cannot exceed what would ordinarily be paid in an arm’s-length transaction for the same services. Excessive compensation is itself an act of self-dealing. The foundation should document the basis for the compensation, obtain comparable data from similar organizations, and have the board formally approve the arrangement. Failure to follow this process can turn a legitimate payment into a costly excise tax violation.

What is a jeopardizing investment under IRC Section 4944?

A jeopardizing investment is one that the foundation managers made without exercising ordinary business care and prudence. Specifically, the IRS looks at whether the investment would jeopardize the foundation’s ability to carry out its charitable purpose. Common examples include highly speculative investments, undiversified portfolios, or investments in startup companies run by disqualified persons. The initial excise tax is 10% of the amount invested, imposed on both the foundation and on any manager who knowingly approved the investment. If the investment is not removed or corrected, the IRS can impose an additional 25% tax. Program-related investments (PRIs) — such as below-market loans to low-income housing projects — are specifically exempt from this rule.

How does the One Big Beautiful Bill Act (OBBBA) affect private foundations in 2026?

The One Big Beautiful Bill Act, signed in mid-2025, introduced significant changes to individual charitable deduction rules for 2026. Specifically, the OBBBA created a new above-the-line charitable deduction for non-itemizers and placed new floors on how much itemizers can deduct for charitable contributions. However, these changes affect the donors who contribute to private foundations — not the foundation’s own excise tax obligations under IRC Chapter 42. The excise tax on private foundations’ net investment income remains at 1.39% for 2026, unchanged by the OBBBA. Foundation managers should consult their advisors to understand how the OBBBA’s donor deduction changes might affect their fundraising strategies and contribution levels going forward.

What is the penalty for a private foundation that files Form 990-PF late?

A private foundation that fails to file Form 990-PF on time faces a penalty of $20 per day for each day the return is late. The maximum penalty per return is the lesser of $10,500 or 5% of the foundation’s gross receipts. For large foundations (those with gross receipts exceeding $1,067,000), the penalty increases to $105 per day, with a maximum of $54,000 per return. In addition, if a foundation fails to file for three consecutive years, the IRS will automatically revoke its tax-exempt status. Reinstatement requires a new application and payment of the retroactive tax. Foundations should always file on time — or request an extension using Form 8868 before the due date.

Last updated: May, 2026