An irrevocable trust can last anywhere from roughly 80 years to forever, depending on which state’s law governs it. States that still follow the traditional common-law time limit cap trust duration at a lifetime plus 21 years, which usually works out to 80 or 90 years in practice. More than 20 states have thrown that limit out entirely and allow trusts to continue for 1,000 years or indefinitely. Within whatever ceiling state law provides, the trust document itself decides when the trust actually terminates, and that endpoint is usually the one that matters.
The Traditional Ceiling: Life in Being Plus 21 Years
For centuries, the common-law Rule Against Perpetuities kept trusts from tying up property indefinitely. Every interest in trust property had to become fully owned by someone within the lifetime of a person alive when the trust was created, plus 21 years after that person’s death. If there was even a theoretical possibility that an interest might fail to vest within that window, the interest was void from the start.
Applied to a real trust, that often meant a duration of 80 or 90 years: the remaining life of the youngest person alive at the trust’s creation, plus the extra 21. The rule worked for a long time, but its all-or-nothing test could void interests that were almost certain to vest on schedule, based on far-fetched hypotheticals.
How States Have Changed the Ceiling
Almost no state applies the rule in its original form today. The reforms fall into three groups, and each one produces a different maximum lifespan.
Wait-and-See
Several states swapped the “what might happen” test for a practical one. Courts wait to see whether the interest actually vests within the allowed period. If it does, it stands, regardless of how the hypothetical analysis would have looked at the outset.
A Fixed 90-Year Period
Many states adopted the Uniform Statutory Rule Against Perpetuities. It keeps the wait-and-see idea and adds a clean alternative: a trust interest is valid so long as it vests or terminates within 90 years of creation. If an interest hasn’t resolved by then, a court reforms the trust to match the grantor’s intent as closely as it can within the 90-year window.
Full Abolition
The biggest shift is that more than 20 states have either abolished the Rule Against Perpetuities or extended the permissible duration to 1,000 years or more. In those states, a trust can continue for as many generations as its assets can support. You don’t have to live in one of these states to use its law. Trusts are routinely set up under the law of a permissive state no matter where the grantor resides.
Dynasty Trusts and Forever Duration
The states that eliminated the perpetuities rule made dynasty trusts possible. A dynasty trust is an irrevocable trust designed to hold wealth across many generations with no built-in end date. In the right jurisdiction, it can theoretically last forever.
The appeal is not just longevity. Because the trust owns the assets rather than any individual beneficiary, those assets stay out of every beneficiary’s taxable estate at death. Wealth passes from grandparent to grandchild to great-grandchild without the 40% federal estate tax taking a cut at each generation.
The generation-skipping transfer tax was created to stop exactly that kind of multi-generational planning, but the law also provides an exemption. In 2026, each person can shelter up to $15 million from the GST tax by allocating their exemption to trust assets, and the GST exemption amount matches the basic exclusion amount used for estate tax purposes.1Office of the Law Revision Counsel. 26 USC 2631 – GST Exemption That $15 million figure was made permanent by the One Big Beautiful Bill Act (P.L. 119-21), passed as part of the FY2025 reconciliation process. Prior law would have cut the exemption roughly in half after 2025.2Congress.gov. The Generation-Skipping Transfer Tax (GSTT) The basic exclusion amount is now set at $15,000,000, with inflation adjustments beginning for decedents dying after 2026.3Office of the Law Revision Counsel. 26 US Code 2010 – Unified Credit Against Estate Tax
Once the exemption is allocated to a dynasty trust, all future growth on those assets is also sheltered. A $15 million trust that doubles to $30 million stays fully exempt. A married couple can each use their own exemption.1Office of the Law Revision Counsel. 26 USC 2631 – GST Exemption
What the Trust Document Actually Sets
State law fixes the outer ceiling. The trust document fixes the real endpoint, and for most trusts that endpoint comes well before any perpetuities deadline. A trust written in a state that allows perpetual duration will still terminate early if the document says it does.
Termination provisions usually follow one of a few patterns:
- Life-based triggers, where the trust ends when a named person dies, often the grantor’s last surviving child or grandchild.
- Age-based triggers, where the trust ends when a beneficiary reaches a specified age and receives the remaining assets outright.
- Event-based triggers, such as the sale of a family business held inside the trust, or a set number of years passing after creation.
- Exhaustion, meaning the trust simply runs out of assets after distributions and administrative costs.
Well-drafted trusts often use staggered distributions, releasing a portion at age 25, more at 30, and the balance at 35, with the trust ending after the final payout. Dynasty trusts are deliberately written the other way, naming successor beneficiaries across generations and giving trustees broad discretion to distribute without ever fully emptying the trust.
Ways an Irrevocable Trust Can End Early
Despite the word “irrevocable,” a trust doesn’t have to run until it hits state-law limits or its own termination clause. Several paths can end it sooner.
Agreement of All Parties
In most states, an irrevocable trust can be modified or terminated if the grantor (if still living) and every beneficiary agree unanimously. This usually requires a court petition. The Uniform Trust Code, adopted in some form by a majority of states, permits this even when termination conflicts with a core purpose of the trust. The unanimous-consent requirement is the hard part when several generations of beneficiaries are involved.
Court-Ordered Termination
A judge can dissolve a trust when circumstances have changed so much that continuing it would defeat the grantor’s original purpose, or when the trust’s objectives have become impossible or illegal to carry out. Courts require a strong showing before overriding the terms the grantor wrote.
Uneconomic Trusts
When assets have shrunk to the point that administrative costs consume an unreasonable share of what’s left, the trustee can often wind the trust down without court involvement. Some states set a specific dollar threshold, with $100,000 being one figure used in state law. Below that, the trustee can terminate after notifying beneficiaries and distribute the remaining assets in a way consistent with the trust’s original purpose.
Extending a Trust Through Decanting
The clock can also run in the other direction. Decanting lets a trustee move assets from an existing irrevocable trust into a new one with different terms, potentially including a longer duration. A trustee might decant a trust that’s approaching its termination date into a new trust governed by the law of a state that allows perpetual duration, effectively restarting the clock.
Most states now authorize decanting by statute, but the rules on what can and cannot be changed vary. The applicable state law has to permit it, and the trustee has to work within the specific statute. Decanting is especially useful when a trust was created before its state abolished the Rule Against Perpetuities and the family wants to take advantage of the newer law. It also comes up when a beneficiary is about to hit the age that would trigger outright distribution, and everyone would rather keep the protective structure in place.
A Tax Trade-Off That Comes With Long Duration
Keeping a trust running for a long time has a cost that catches families off guard. When an irrevocable trust distributes appreciated assets during the grantor’s lifetime, the recipients generally take the trust’s original cost basis, not the current market value. If the trust bought stock for $100,000 and it’s worth $500,000 at distribution, the beneficiary’s basis is $100,000, and selling means paying capital gains on the $400,000 gain.
Property that passes through a decedent’s estate typically receives a stepped-up basis to fair market value at death under IRC Section 1014, which can eliminate capital gains tax on the appreciation.4Office of the Law Revision Counsel. 26 US Code 1014 – Basis of Property Acquired From a Decedent Assets held in an irrevocable trust generally do not qualify for that step-up when the grantor dies, unless the assets are actually included in the grantor’s taxable estate. In Revenue Ruling 2023-2, the IRS confirmed that being treated as a grantor trust for income tax purposes is not enough on its own.
The trade-off is real. A dynasty trust keeps assets out of every beneficiary’s estate and avoids the 40% estate tax at each generation, but the same exclusion means the assets never get a basis reset. Over several generations, the gap between cost basis and market value can grow very large, and so can the embedded capital gains liability. The IRS has also taken the position in private letter rulings that terminating a trust can itself trigger capital gains recognition. Families thinking about early termination to capture a basis step-up should work through the numbers before acting.