The Rule Against Perpetuities is a property law principle that limits how long a dead person can control who ends up owning their property. In its traditional form, it voids any future ownership interest that isn’t guaranteed to become final within the lifetime of someone alive when the interest was created, plus 21 years. If there’s any possibility the ownership question could still be open past that deadline, the gift is treated as void from the moment it was made. Most states have reformed or abolished the rule, but it still shapes how trusts and wills are drafted and how courts read older documents.
The Three Pieces That Make the Rule Work
The rule hinges on three ideas: vesting, a measuring life, and a 21-year tail added to the end.
A property interest “vests” when the person who will receive it is identified and their right to it becomes unconditional. Before that, the interest is contingent on something that hasn’t happened yet, like a grandchild reaching a certain age. The rule only targets contingent interests. Anything that vests immediately is safe.
A “life in being” is any person alive or already conceived at the moment the interest is created. For a will, that moment is the writer’s death. For a trust or deed made during life, it’s the date the document takes effect. A group can serve as the measuring lives, such as “my children,” but only if no new members can join the group after the interest is created.1Legal Information Institute. Lives in Being
After the last measuring life ends, the rule tacks on a fixed 21 years. That number roughly tracks the age of majority, giving a minor time to grow up and claim an inheritance. If the interest hasn’t either vested or clearly failed by the end of the combined window, the traditional rule kills it.
How a Violation Actually Happens
Picture a will that leaves a family farm “to my son for his life, then to the first of my grandchildren who reaches age 25.” The son has a life estate. The grandchild’s interest is contingent on hitting 25. The question is whether we can guarantee some grandchild will either reach 25 or fail to reach 25 within the perpetuity period.
Here’s where the rule turns harsh. The son could have another child after the will’s creator dies. Then the son and every other family member alive at the creator’s death could die the next day. That new grandchild, born after the will took effect, wouldn’t turn 25 for another 25 years, which is more than 21 years after the last measuring life ended. Because that scenario is technically possible, the entire gift to the grandchildren fails under the traditional rule.
The law doesn’t wait to see what actually happens. It runs every hypothetical at the moment the interest is created, and if any scenario produces a violation, the interest is dead on arrival. This produces some famously absurd results, including the “fertile octogenarian” fiction that treats an 80-year-old as still capable of having children.2Legal Information Institute. Fertile-Octogenarian Rule
What Happens When an Interest Is Struck Down
Under the traditional common law version, the penalty is absolute. A violating interest is void from the instant it was created. Courts don’t rewrite the language or give the creator another chance. The offending clause is treated as though it were never written.
When a future interest is wiped out, the property falls back into the creator’s estate. From there it passes through whatever catch-all provision the will contains. If there isn’t one, the property goes to the creator’s heirs under the state’s default inheritance rules. The people the creator wanted to benefit get nothing, and the property often ends up somewhere no one intended.
A single drafting mistake can unravel an entire estate plan, sometimes wiping out gifts worth millions. That severity is a big part of why most states have moved away from the traditional rule.
How States Have Changed the Rule
Reform efforts have generally gone in three directions, and a growing number of states have simply abolished the rule for most trusts.
Wait and See
The most intuitive fix is the “wait-and-see” approach. Instead of voiding an interest based on what might happen, the court lets the clock run and checks whether the interest actually vests within the perpetuity period. If a grandchild does reach 25 in time, the gift stands. The interest is only killed if the deadline actually passes without vesting. Hypothetical absurdities disappear because courts judge real events.
The Uniform Statutory Rule Against Perpetuities
The Uniform Statutory Rule Against Perpetuities, known as USRAP, pushes wait-and-see further. An interest is valid if it either satisfies the traditional common law rule or actually vests or terminates within 90 years of its creation. The flat 90-year window replaces the hunt for specific measuring lives. If the interest still hasn’t vested after 90 years, a court can reform the document to carry out the creator’s wishes as closely as possible within the deadline.3California Law Revision Commission. Uniform Statutory Rule Against Perpetuities
Cy Pres and Judicial Reformation
Even outside USRAP, some courts can reform a violating interest under the cy pres doctrine, a phrase meaning “as near as possible.” Rather than voiding a gift, the court rewrites the problem language to honor the creator’s intent while fitting within the rule. In the farm example, a judge might cut the age requirement from 25 to 21, which guarantees the interest vests within 21 years of the son’s death. The gift survives.
States That Have Abolished the Rule
A significant number of states have repealed the rule altogether, at least for certain trusts. These states allow “dynasty trusts” that can theoretically last forever, passing wealth from generation to generation without the forced termination the rule was designed to impose. The list has grown steadily. If you’re setting up a long-term trust, the state where it’s established matters enormously, because a trust that is perfectly legal in one state can violate the rule in another.
Dynasty Trusts and the Tax Angle
Abolition created a powerful planning tool but also a tax question. Before the generation-skipping transfer tax existed, wealthy families used trusts to skip estate taxes at every generation by passing assets directly to grandchildren, great-grandchildren, and beyond. The generation-skipping transfer tax closes that gap by imposing a tax when trust assets pass to someone two or more generations below the person who created the trust.4Congress.gov. The Generation-Skipping Transfer Tax (GSTT)
Each person gets a lifetime exemption from that tax. For 2026, the exemption is $15,000,000, after Congress made the higher exemption permanent and slightly increased it.5Internal Revenue Service. What’s New – Estate and Gift Tax Assets placed into a dynasty trust up to that amount can grow and pass to future generations free of both the estate tax and the generation-skipping transfer tax. In a state that has abolished the rule, the shelter can theoretically run indefinitely. One trap worth knowing: the generation-skipping exemption is not portable between spouses, so a surviving spouse cannot pick up an unused portion the way they can with the regular estate tax exemption.4Congress.gov. The Generation-Skipping Transfer Tax (GSTT)
Savings Clauses
Experienced estate planning attorneys almost always include a “perpetuities savings clause” in trusts and wills. It is a backstop that forces the trust to end before it could possibly violate the rule, no matter what hypothetical plays out. The clause typically sets a hard deadline of 21 years after the death of the last survivor of a named group, and then adds an automatic gift that vests immediately if the trust is somehow still running when that deadline hits.6California Law Revision Commission. Recommendation Relating to Uniform Statutory Rule Against Perpetuities
In most cases, the trust ends naturally long before the savings clause ever activates. But if something unexpected happens, the clause keeps the plan from being voided. Any trust or will that creates contingent future interests should contain one, and its absence is a sign the document wasn’t drafted by someone familiar with perpetuities law.
When This Rule Actually Matters to You
For most estates, it doesn’t. A will that leaves everything to your spouse and then equally to your children creates interests that vest immediately at your death. No contingency, no perpetuities problem.
The rule becomes relevant when an estate plan tries to control property across multiple generations or attaches conditions to future gifts. Common triggers include trusts that distribute assets only when beneficiaries reach a specific age, trusts designed to last for the lifetimes of grandchildren or great-grandchildren, gifts to a class of people that might still be growing (such as “all my future descendants”), and property transfers tied to events that might not happen for a long time, if ever.
If you’re working with an attorney on anything beyond a straightforward will, ask specifically how your plan interacts with your state’s version of the rule. The answer depends on whether the state follows the traditional common law, has adopted USRAP, uses wait-and-see, or has abolished the rule. Getting this wrong can void the central gift in your estate plan and send your assets to people you never meant to benefit.