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Trust Accounting and Fiduciary Taxation

Fiduciary income tax rules under Subchapter J of the Internal Revenue Code are highly compressed. For tax year 2026, a non-grantor complex trust hits the top 37% ordinary income tax bracket at just $16,000 of accumulated taxable income, and the top 20% long-term capital gains bracket at $16,250. In addition, the 3.8% Net Investment Income Tax (NIIT) under IRC §1411 applies to undistributed net investment income above these same low thresholds. Because of this compression, strategic coordination between trust accounting and tax planning is necessary to avoid confiscatory taxation.

To manage fiduciary taxes, you must distinguish between two separate concepts:

Trust Accounting Income (TAI): TAI is the fiduciary concept of income determined by the trust instrument and state law under the Uniform Fiduciary Income and Principal Act (UFIPA). TAI defines what is allocated to the current income beneficiaries versus the remainder beneficiaries. By default under the UFIPA, ordinary receipts (interest and dividends) are classified as income, realized capital gains are allocated to principal (corpus), and administration fees (such as trustee and tax preparation fees) are split 50/50 between income and principal.
Distributable Net Income (DNI): DNI is a tax concept defined under IRC §643 that caps the fiduciary’s income distribution deduction and determines the maximum taxable amount (and character) of distributions in the hands of the beneficiaries. DNI is calculated by taking the trust’s taxable income (before the distribution deduction and personal exemption) and subtracting capital gains allocated to principal, then adding back tax-exempt interest (net of allocable expenses).

Fiduciary taxation operates under a conduit system, utilizing the Income Distribution Deduction (IDD) under IRC §651 (for simple trusts) and IRC §661 (for complex trusts):

Simple Trusts: Must distribute all TAI currently, cannot make charitable contributions, and cannot distribute principal. The trust deducts the distributed income up to the DNI limit. The beneficiary reports this income on their individual tax return, and the trust is typically taxed only on retained capital gains.
Complex Trusts: May accumulate income, distribute principal, or make charitable contributions. The trust receives a deduction for actual distributions made during the tax year (or within the first 65 days of the following year under the IRC §663(b) election).

Under IRC §67(e), expenses that are unique to trust administration—including corporate trustee fees, fiduciary accounting fees, and trust legal fees—are fully deductible above-the-line. They are not subject to the suspension of miscellaneous itemized deductions.

Distribute or Accumulate: Making the Decision This is the single recurring decision in administering a non-grantor trust, and it comes up every December. Start by pricing it, because the number is larger than people expect. For a given amount of retained ordinary income $I$ , the annual cost of accumulating versus distributing is the rate spread times the income:

Δ T = I \times [(τ_{trust} + τ_{NIIT}) - τ_{beneficiary}]

where $τ_{trust}$ is the trust’s effective rate—not 37%, because the first $16,000 climbs through the lower brackets—and $τ_{NIIT}$ is 3.8% on the undistributed net investment income above that threshold. Take $100,000 of ordinary investment income in 2026 and a beneficiary in the 24% bracket. Retained in the trust:

\begin{aligned} T_{trust} & = \underset{$ 330}{\underset{⏟}{$ 3, 300 \times 10 %}} + \underset{$ 2, 016}{\underset{⏟}{($ 11, 700 - $ 3, 300) \times 24 %}} + \underset{$ 1, 505}{\underset{⏟}{($ 16, 000 - $ 11, 700) \times 35 %}} \\ + \underset{$ 31, 080}{\underset{⏟}{($ 100, 000 - $ 16, 000) \times 37 %}} + \underset{$ 3, 192}{\underset{⏟}{($ 100, 000 - $ 16, 000) \times 3.8 %}} = $ 38, 123 \end{aligned}

Distributed instead, the beneficiary pays $$ 100, 000 \times 24 % = $ 24, 000$ and owes no NIIT below the individual threshold. The spread is $14,123 a year—roughly 14 points—on one year of income from a single trust. Over a twenty-year administration, compounded, it is the price of a house.

So distribute, unless one of these is true—and when one is true, accumulate without apology, because you did not build the trust to save 14 points:

The beneficiary cannot be trusted with it: A spendthrift, an active addiction, a bankruptcy, a divorce in progress, a lawsuit. Distributed money is exposed money; the tax saving is worth nothing against a creditor who takes the whole distribution.
The beneficiary is a minor: Distributions to a minor’s custodial account vest outright at 18 or 21, which is usually the outcome the trust exists to prevent, and the kiddie tax claws back much of the arbitrage anyway.
The beneficiary receives needs-tested benefits: A distribution can cost Medicaid or SSI eligibility worth far more than the tax (section “Special Needs Trusts”).
The beneficiary’s own rate is no better: A high-earning heir already in the top bracket offers no arbitrage—and if they live in a high-tax state while the trust sits in a no-tax one, distributing can actively cost money (section “The NING and Why It No Longer Works in California”).
The trust is accumulating on purpose: A GST-exempt dynasty trust compounding for the next generation is doing exactly what it should (section “Dynasty Trusts”).

Three levers make the decision easier than it looks. First, it is not annual and irreversible—the IRC §663(b) election lets you distribute within the first 65 days after year-end and treat it as made in the prior year, so you decide in February with the actual Form 1099s in hand instead of guessing in January. Second, the decision is not all-or-nothing: distribute enough to strip the income above the $16,000 threshold and accumulate the rest, capturing most of the spread while keeping most of the protection. Third, if the concern is protection, not the beneficiary’s judgment, consider distributing to a sub-trust for that beneficiary, not directly to them personally—the income is carried out on the K-1 while the assets stay wrapped.

Getting Capital Gains Out of the Trust Distributing income solves only half the problem, because capital gains are normally allocated to principal and therefore stay trapped in the trust—taxed at 20% plus the 3.8% NIIT above $16,250 while your beneficiary may sit in the 0% or 15% bracket. On a $200,000 realized gain that gap is worth $17,600 against a 15% beneficiary and $47,600 against one in the 0% bracket. Treas. Reg. §1.643(a)-3(b) lets you close it: capital gains can be included in DNI, and so carried out to the beneficiary, if the trustee does so consistently under a power in the governing instrument or under local law, or actually distributes the gains, or treats them as distributed in determining the amount paid to the beneficiary. Making this work requires two choices: give the trustee explicit authority in the trust document—retrofitting it later is harder than drafting it now. And be consistent: the regulation demands a reasonable and consistent practice, so a trustee who allocates gains to income only in years it helps is inviting the IRS to unwind the whole pattern.

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