Trustee Duty to Diversify Trust Assets: UPIA Standards and Exceptions

Under the Uniform Prudent Investor Act, the trustee’s duty to diversify trust assets is a default requirement to spread holdings across different investments so a single loss cannot sink the trust. Diversification is mandatory unless the trust document says otherwise or the trustee can reasonably show that special circumstances make concentration the better choice. A trustee who ignores the duty is personally on the hook for losses that diversification would have prevented.

What the Uniform Prudent Investor Act Requires

The core rule sits in Section 3 of the UPIA: “A trustee shall diversify the investments of the trust unless the trustee reasonably determines that, because of special circumstances, the purposes of the trust are better served without diversifying.”¹ The verb is “shall.” Diversification is the default; concentration is the exception, and the burden to justify it falls on the trustee.

The broader standard in Section 1 tells the trustee to invest “as a prudent investor would, by considering the purposes, terms, distribution requirements, and other circumstances of the trust.”¹ That standard asks for reasonable care, skill, and caution rather than maximum growth or absolute safety.

One feature of the UPIA matters more than any other when a trustee’s conduct ends up in court: performance is judged portfolio-wide, not investment by investment. A court looks at whether the overall strategy had risk and return objectives suited to the trust.² One losing stock inside a sensible portfolio is not a breach. A portfolio concentrated in one stock with no plan and no explanation almost certainly is.

The prudent investor rule is a default rule. The person who creates the trust can expand it, limit it, or override it through the trust’s own terms, and a trustee acting in reasonable reliance on those terms is protected.¹ Reading the trust document is therefore step one before any investment decision gets made.

Factors the Trustee Must Weigh

Section 2(c) of the UPIA lists eight factors the trustee has to consider when investing and managing trust assets:¹

General economic conditions, including interest rates and market cycles.
The possible effect of inflation or deflation on long-term purchasing power.
Tax consequences of each investment decision.
The role each investment plays within the overall portfolio.
Expected total return, from both income and capital appreciation.
Other resources available to the beneficiaries outside the trust.
Needs for liquidity, regular income, and preservation of capital.
Any special value an asset has to the trust’s purpose or to the beneficiaries.

The trustee also has an independent duty to verify the facts behind each decision rather than relying on stale statements or assumptions.¹ A trustee who inherits a portfolio heavy in one company’s stock and never checks the concentration because the account “looked fine last quarter” has already fallen short.

When a Trustee Can Keep a Concentrated Position

Two things can override the diversification requirement.

The first is the trust document itself. If the settlor explicitly authorized the trustee to retain a specific asset, such as shares in a family business, a block of founder stock, or a particular piece of real estate, the trustee is generally protected from claims that the portfolio is too concentrated. These retention clauses reflect the settlor’s judgment that preserving the asset matters more than textbook diversification, and courts honor them because the UPIA is a default rule the settlor can modify.¹

The second is the special-circumstances exception in Section 3 itself. The trustee must “reasonably determine” that the trust’s purposes are better served without diversifying.¹ Examples that can qualify include a historic property tied to a charitable purpose, voting shares that give the family continued control of a business, or a position with such large built-in capital gains that selling would destroy more value than diversification would protect.

The analysis has to be real and documented. “We’ve always held this stock” is not a special circumstance. “Selling would trigger a seven-figure tax bill and cost the family its board seat, and here is how we weighed that against the risk” might be.

The Initial Review After You Take Over

Section 4 requires a trustee to review the trust’s assets within a reasonable time after accepting the role and to make decisions about what to keep and what to sell to bring the portfolio in line with the trust’s purposes and the Act’s requirements.¹ The Act does not pick a specific deadline, because “reasonable” depends on the complexity of the assets, the size of the trust, and conditions in the market at the time.

This is where new trustees most often get into trouble. A common pattern: a parent dies leaving a trust funded almost entirely with one company’s shares. The successor trustee, usually a family member, assumes the shares should stay because they mattered to the parent. Months pass. The stock drops 40%. A beneficiary sues. Courts in those cases look at when a prudent trustee would have started selling, and they typically expect meaningful diversification to begin within the first few months of taking over, with the bulk of a concentrated holding reduced relatively quickly.

The same eight factors from Section 2(c) govern this initial review. Document the analysis, set a target allocation, and start executing. Waiting for a “better time to sell” without a written rationale is the kind of inaction that leads to personal liability.

The Tax Tension in Selling a Concentrated Position

Trusts are taxed on a dramatically compressed schedule compared to individuals. For 2026, trust and estate income reaches the top 37% rate at just $16,000 of taxable income, and long-term capital gains hit the 20% rate above $16,250.³ The 3.8% Net Investment Income Tax applies to undistributed net investment income once the trust’s adjusted gross income exceeds the threshold for the top bracket.⁴ Long-term gains inside the trust can therefore face a combined rate approaching 23.8% very quickly.

That creates a genuine problem for a trustee holding a concentrated low-basis position. Dumping the whole position in one tax year can push the trust to the top of every bracket at once. Phased selling across multiple years, distributing income to beneficiaries so it is taxed at their personal rates, or combining both approaches often reduces the total tax cost while still achieving diversification within a defensible timeframe. The point is not that taxes excuse delay. The point is that the pace of diversification is itself a decision the trustee should think through and document.

Delegating to a Financial Professional

Most individual trustees are not investment professionals, and the UPIA accounts for that. Section 9 lets a trustee delegate investment and management functions to an outside agent such as a registered investment advisor or a bank trust department.¹ To avoid personal liability for the agent’s decisions, the trustee has to do three things:

Select the agent carefully, considering qualifications, track record, resources, and fees against the trust’s size and complexity.
Put the scope of the delegation in writing, consistent with the trust’s purposes.
Monitor the agent’s performance periodically to confirm the approach still matches the delegation terms and the trust’s needs.

A trustee who does all three is not liable for the agent’s individual investment picks.¹ Delegation is not abdication, though. A trustee who hires an advisor, signs the paperwork, and never looks at a statement has failed the monitoring step and is back on the hook.

The reverse also holds. A trustee with professional investment skills, or one who was appointed because they claimed those skills, is held to a higher standard than a family member with no financial background.¹ A corporate trustee cannot plead ignorance about portfolio concentration the way an uncle named in a will might.

Document Everything in an Investment Policy Statement

The strongest protection against a breach claim is a written record showing the reasoning behind each major investment decision. The standard tool is an Investment Policy Statement, which generally covers:

The trust’s investment objectives, time horizon, and goals for each class of beneficiary.
Risk tolerance, expressed in terms the trustee can actually apply.
Target asset allocation across stocks, bonds, cash, real estate, and other classes, with reasoning.
Rebalancing triggers, whether by calendar, by percentage drift, or both.
Criteria for selecting individual investments, including benchmarks and expense limits.
A monitoring schedule for performance review.

The IPS is the document a court will ask to see when a beneficiary challenges investment decisions. A trustee who can point to a written policy, show that it was followed, and show that it was updated as conditions changed is in a much stronger position than one reconstructing their thinking after a loss. The IPS also anchors any delegation to an outside advisor, because it defines the scope the UPIA requires the trustee to spell out in writing.

What Happens If a Trustee Fails to Diversify

When a trustee breaches the duty to diversify and the trust loses money because of it, the primary remedy is a surcharge. The trustee personally repays the trust for the loss. Courts generally measure damages as the amount needed to put the trust where it would have been without the breach, or the profit the trustee made from the breach, whichever is greater, with interest added at the legal rate for judgments in that jurisdiction.

In a concentrated-stock case, the calculation usually works by identifying a date by which a prudent trustee would have started selling, backing out the capital gains tax that would have been due, compounding the hypothetical reinvested proceeds at a reasonable rate over the relevant period, and subtracting the dividends actually received and the remaining value of the stock. The resulting number can be large, especially when a declining stock was held for years while the broader market rose.

Courts have other tools beyond money damages. They can:

Remove the trustee and appoint a replacement.
Reduce or deny the trustee’s compensation for the period of the breach.
Suspend the trustee while litigation plays out.
Order a formal accounting of trust assets.
Void specific transactions or impose a lien on wrongfully handled property.

Doing nothing is itself a decision, and it is the decision courts punish most sharply. A trustee who inherits a concentrated portfolio, recognizes the risk, builds a diversification plan, and executes it at a defensible pace is far less exposed than one who lets inertia run the trust. And if the concentrated position happens to perform well, that does not retroactively make the choice prudent. The duty is measured by the process, not the outcome.

1
Uniform Law Commission. Uniform Prudent Investor Act of 1994
2
Legal Information Institute. Uniform Prudent Investor Act
3
Internal Revenue Service. 2026 Form 1041-ES
4
Internal Revenue Service. Topic No. 559, Net Investment Income Tax