Distributable and Undistributed Net Income in Trust Taxation

In trust taxation, distributable net income (DNI) sets the ceiling on how much trust income can be taxed to beneficiaries in any given year, and undistributed net income (UNI) is whatever slice of DNI the trust keeps rather than pays out. The distinction drives the entire tax bill. For 2026, a trust that retains income hits the top federal rate of 37% once taxable income crosses just $16,000; a single individual doesn’t reach that rate until $640,600.¹ That gap is why fiduciaries spend so much time on the DNI calculation: it decides whether income gets taxed at the trust’s compressed rates or at a beneficiary’s much lower personal rates.

How DNI Is Calculated

DNI starts with the trust’s taxable income and then makes several adjustments unique to fiduciary accounting. The figure is defined by statute and functions as a cap in both directions: beneficiaries cannot be taxed on more than DNI, and the trust cannot deduct more than DNI for the distributions it makes.²

The core adjustments:

Tax-exempt interest gets added back. Income from municipal bonds is excluded from taxable income, but it is included in DNI because it is still available to distribute. It keeps its tax-free character when it reaches the beneficiary.²
Capital gains are usually excluded. When a trust sells an asset at a profit, that gain stays in principal and is taxed at the trust level, unless the trust document requires distribution of gains or the fiduciary actually pays them out during the year.²
The distribution deduction is removed. Because DNI is used to calculate that deduction, including it would create a circular calculation.

The character of the income carries through the whole calculation. If DNI consists of 60% ordinary interest and 40% qualified dividends, those proportions flow to the beneficiary, who then reports the qualified dividends at capital gains rates on a personal return. Fiduciaries complete Schedule B of Form 1041 to run the calculation.³

Expenses That Reduce DNI

Administrative costs shrink the income available to distribute and therefore lower DNI. Trustee compensation, legal fees for trust administration, and accounting costs all reduce the trust’s taxable income before DNI is figured.

Miscellaneous itemized deductions are no longer allowed for any taxpayer, and that suspension is now permanent. Costs unique to trust administration, however, are treated differently: they are adjustments to adjusted gross income rather than itemized deductions, so they survive the suspension.⁴ Trustee fees are the clearest example. Investment advisory fees are the kind of expense an individual would also incur, so they fall under the suspension and are not deductible.

When a trust holds both taxable and tax-exempt investments, the fiduciary must allocate expenses between the two. The portion tied to tax-exempt income is not deductible, which slightly increases DNI. It is easy to overlook and can meaningfully move the final number.

How Distributed Income Is Taxed to Beneficiaries

Trust taxation runs on a conduit principle: income that reaches the beneficiary is taxed to the beneficiary, not the trust. The trust claims a distribution deduction that offsets its own income, and the same amount lands on the beneficiary’s personal return instead.

For a simple trust, the deduction equals income required to be distributed currently, capped at DNI.⁵ For a complex trust, it covers both required distributions and any other amounts the fiduciary actually pays out, again capped at DNI.⁶ A trust that distributes all its income can zero out its own tax liability.

Each beneficiary receives Schedule K-1 (Form 1041) showing the types and amounts of income to report on Form 1040.⁷ Character carries through: qualified dividends stay qualified dividends, tax-exempt interest stays tax-exempt. The beneficiary then pays at personal rates.

What Counts as Undistributed Net Income

Undistributed net income is what is left of DNI after the fiduciary accounts for actual payouts. The statutory formula takes DNI, subtracts distributions (both mandatory and discretionary), and then subtracts the federal income taxes the trust paid on that retained income.⁸

Tracking UNI year over year matters because it represents income that was eligible for distribution but stayed in the trust. For domestic trusts, the immediate concern is straightforward: the trust already paid tax on this income at compressed rates, and the fiduciary needs clear records of how much accumulated income exists and how much tax has been paid on it. Accumulated amounts distributed in later years are treated as nontaxable returns of principal once the current year’s DNI is exhausted, at least for domestic trusts created after March 1, 1984.⁸

Why Retained Trust Income Is So Heavily Taxed

The trust brackets for 2026 are deliberately compressed:

10% on the first $3,300 of taxable income
24% on income from $3,301 to $11,700
35% on income from $11,701 to $16,000
37% on income above $16,000

An individual filing single doesn’t reach 37% until taxable income tops $640,600.¹ A trust earning $50,000 in retained income pays the top rate on more than two-thirds of it. The same income distributed to a beneficiary at a moderate income level might be taxed at 22% or 24%. That is the concrete reason fiduciaries push income out whenever the trust document allows.

Layered on top is the 3.8% Net Investment Income Tax on undistributed investment income once the trust’s adjusted gross income exceeds the threshold where the top bracket begins. For 2026 that threshold is $16,000. The NIIT applies to the lesser of the trust’s undistributed net investment income or the amount by which AGI exceeds the threshold. Grantor trusts and charitable trusts are exempt.⁹ Combined with the 37% bracket, a trust retaining investment income can face an effective federal rate above 40%.

The 65-Day Election

Fiduciaries of complex trusts have a timing tool worth knowing. They can elect to treat distributions made within the first 65 days of a new tax year as if the payments were made on the last day of the prior year.¹⁰ For a calendar-year trust, distributions made by March 6, 2027 can be counted as 2026 distributions.

This matters because the fiduciary often will not know the trust’s final income until after year-end, when statements arrive and the accountant runs the numbers. The 65-day window gives room to decide whether pushing income out saves more in tax than keeping it. The election cannot exceed the greater of the trust’s accounting income or its DNI for the year, reduced by amounts already distributed during the year.¹¹

To make it, the fiduciary checks the box for Question 6 in the “Other Information” section of Form 1041.³ The return must be filed by its due date, including extensions, and once made the election is irrevocable for that year.

When DNI Rules Do Not Apply

Not every trust uses DNI at all. If the grantor retains enough control over the assets, federal tax law treats the grantor as the owner for income tax purposes, and the trust’s income, deductions, and credits flow directly to the grantor’s personal return.¹² The trust does not file a separate return claiming a distribution deduction, and beneficiaries do not receive K-1s. If you are administering a revocable living trust or another arrangement where the grantor kept significant powers, the DNI framework does not apply.

Multiple Beneficiaries and the Tier System

When a complex trust has more than one beneficiary and total distributions exceed DNI, the tax code uses a two-tier system to decide who gets taxed on what.

Tier 1 covers income the trust document requires to be distributed currently. If mandatory distributions to all beneficiaries exceed DNI, each beneficiary reports a proportional share of DNI based on their share of the required distributions.¹³
Tier 2 covers discretionary distributions. Any DNI left after Tier 1 is allocated among beneficiaries who received discretionary payments, again proportionally if those distributions exceed the remaining DNI.¹³

Anything a beneficiary receives beyond what DNI supports is a nontaxable distribution of principal. Because Tier 1 always absorbs DNI first, Tier 2 beneficiaries are more likely to receive tax-free principal.

Foreign Trust Throwback

Domestic trusts created after March 1, 1984 are generally exempt from throwback rules. Foreign trusts are not. When a foreign trust distributes more than its current-year DNI, the excess is traced back to prior years’ undistributed net income, and the beneficiary is taxed as if that income had been distributed in the year it was earned, at those earlier years’ rates.¹⁴ An interest charge is added to compensate for the years of deferral.

Filing and Estimated Payments

A calendar-year trust files Form 1041 and delivers Schedule K-1 to each beneficiary by April 15.³ An extension delays the return, not the tax.

If the trust expects to owe at least $1,000 after withholding and credits, the fiduciary must make quarterly estimated payments due April 15, June 15, September 15, and January 15 of the following year.¹⁵ Missing an installment can trigger an underpayment penalty even if the trust ultimately receives a refund. Late payment of tax owed carries a penalty of 0.5% of the unpaid balance for each month it remains outstanding.¹⁶ Fiduciaries retaining significant trust income should set up a quarterly payment schedule from trust assets with a tax professional.

1
Tax Foundation. 2026 Tax Brackets and Federal Income Tax Rates
2
Office of the Law Revision Counsel. 26 USC 643 – Definitions Applicable to Subparts A, B, C, and D
3
Internal Revenue Service. Instructions for Form 1041 and Schedules A, B, G, J, and K-1
4
Office of the Law Revision Counsel. 26 US Code 67 – 2-Percent Floor on Miscellaneous Itemized Deductions – Section: (e)
5
Office of the Law Revision Counsel. 26 USC 651 – Deduction for Trusts Distributing Current Income Only
6
Office of the Law Revision Counsel. 26 USC 661 – Deduction for Estates and Trusts Accumulating Income or Distributing Corpus
7
Internal Revenue Service. Instructions for Schedule K-1 (Form 1041) for a Beneficiary Filing Form 1040 or 1040-SR
8
Office of the Law Revision Counsel. 26 USC 665 – Definitions Applicable to Subpart D
9
Internal Revenue Service. Instructions for Form 1041 and Schedules A, B, G, J, and K-1
10
Office of the Law Revision Counsel. 26 USC 663 – Special Rules Applicable to Sections 661 and 662
11
eCFR. 26 CFR 1.663(b)-1 – Distributions in First 65 Days of Taxable Year
12
Office of the Law Revision Counsel. 26 USC 671 – Trust Income Attributable to Grantors and Others
13
Office of the Law Revision Counsel. 26 US Code 662 – Inclusion of Amounts in Gross Income of Beneficiaries of Estates and Trusts Accumulating Income or Distributing Corpus
14
Office of the Law Revision Counsel. 26 USC 667 – Treatment of Amounts Deemed Distributed by Trust in Preceding Years
15
Internal Revenue Service. 2026 Form 1041-ES
16
Internal Revenue Service. Failure to Pay Penalty