UBE Future Interests and the Rule Against Perpetuities

Last updated: May 2, 2026

Future Interests and the Rule Against Perpetuities questions are one of the highest-leverage areas to study for the UBE. This guide breaks down the rule, the elements you need to recognize, the named traps that catch most students, and a memory aid that scales to test day. Read it once, then practice the same sub-topic adaptively in the app.

The rule

A future interest is a presently existing property right that entitles the holder to possession (or a chance at possession) at some point in the future. Future interests are sorted first by who holds them — the grantor (reversion, possibility of reverter, right of entry) or a third-party transferee (remainder or executory interest) — and then by their qualities (vested, contingent, vested subject to open, vested subject to complete divestment). The common-law Rule Against Perpetuities (RAP) voids any contingent remainder, executory interest, or vested remainder subject to open if it might vest or fail to vest more than 21 years after the death of some life in being at the creation of the interest. RAP applies only to those three interest types; reversions, possibilities of reverter, rights of entry, and indefeasibly vested remainders are exempt.

Elements breakdown

Reversion

A future interest retained by the grantor when the grantor conveys a vested estate of lesser quantum than the grantor held.

  • Held by grantor
  • Follows estate of lesser duration
  • Automatically becomes possessory
  • Not subject to RAP

Common examples:

  • O, holding fee simple, conveys 'to A for life' — O retains a reversion in fee simple.

Possibility of Reverter

The future interest automatically retained by a grantor who conveys a fee simple determinable.

  • Held by grantor
  • Follows fee simple determinable
  • Vests automatically on condition
  • Durational language ('so long as,' 'until,' 'while')
  • Not subject to RAP

Common examples:

  • O conveys 'to A so long as the land is used as a school.'

Right of Entry (Power of Termination)

The future interest retained by a grantor who conveys a fee simple subject to condition subsequent; grantor must affirmatively reclaim.

  • Held by grantor
  • Follows fee simple subject to condition subsequent
  • Conditional language ('but if,' 'provided that')
  • Must be expressly reserved
  • Requires affirmative re-entry
  • Not subject to RAP

Common examples:

  • O conveys 'to A, but if liquor is sold on the premises, O may re-enter and retake.'

Indefeasibly Vested Remainder

A remainder created in an ascertained, living person that is certain to become possessory and is not subject to any condition precedent or divestment.

  • Created in transferee
  • Follows natural end of prior estate
  • Holder ascertained and in being
  • No condition precedent
  • Not subject to divestment
  • Not subject to RAP

Common examples:

  • 'To A for life, then to B' (B is alive and identified).

Vested Remainder Subject to Open (Class Gift)

A remainder given to a class of takers, at least one of whom is ascertained and qualified, but the class can still grow.

  • Created in a class
  • At least one member ascertained
  • Class remains open
  • Subject to RAP
  • Class closes under the rule of convenience or by physiological cutoff

Common examples:

  • 'To A for life, then to A's children,' where A has one living child but could have more.

Vested Remainder Subject to Complete Divestment

A remainder that is vested but can be cut short by the happening of a condition subsequent.

  • Created in ascertained transferee
  • No condition precedent
  • Subject to condition subsequent
  • Defeasance shifts to executory interest
  • Not subject to RAP (when not class gift)

Common examples:

  • 'To A for life, then to B, but if B does not survive A, then to C' — B has a vested remainder subject to complete divestment; C has a shifting executory interest.

Contingent Remainder

A remainder created in an unascertained taker or subject to a condition precedent.

  • Created in transferee
  • Follows natural end of prior estate
  • Either taker unascertained OR condition precedent unmet
  • Subject to RAP

Common examples:

  • 'To A for life, then to A's first child to reach 25.' If no child has reached 25, the remainder is contingent.

Shifting Executory Interest

A future interest in a transferee that, on the happening of a stated event, divests another transferee's estate.

  • Created in transferee
  • Cuts short prior transferee's estate
  • Triggered by stated condition
  • Subject to RAP

Common examples:

  • 'To A, but if A ever sells alcohol on the land, then to B.'

Springing Executory Interest

A future interest in a transferee that divests the grantor's retained interest after a gap in possession.

  • Created in transferee
  • Cuts short grantor's interest
  • Possession springs from grantor
  • Subject to RAP

Common examples:

  • 'To A when A graduates from law school' — O retains until A graduates, then A's interest springs.

Common-Law Rule Against Perpetuities

No interest is good unless it must vest, if at all, no later than 21 years after the death of some life in being at the creation of the interest.

  • Applies only to contingent remainders, executory interests, vested remainders subject to open
  • Measured at moment interest is created
  • Validating life must be alive at creation
  • Interest must necessarily vest or fail within life + 21 years
  • Any possibility of remote vesting voids interest

Common examples:

  • Fertile octogenarian, unborn widow, slothful executor, and magic gravel pit are the four classic RAP traps.

Common patterns and traps

The Comma Test for Vested-vs-Contingent

Examiners drop a single conditional clause and dare you to characterize the remainder. If the condition appears inside the granting clause and qualifies the gift itself, the remainder is contingent. If the gift is given clean and a separate clause threatens to take it away, the remainder is vested subject to complete divestment, and the divesting interest is an executory interest. The classification flips RAP analysis on its head — vested-subject-to-divestment is exempt; contingent and the executory interest are tested.

An answer choice that calls B's interest 'contingent' when the conveyance reads 'to A for life, then to B, but if B predeceases A, then to C.'

Fertile Octogenarian Trap

At common law, every living person — regardless of age, sex, or medical reality — is conclusively presumed capable of having more children. So a class gift to 'A's grandchildren' when A is alive and 92 years old is still tested as if A might have another child, who would then have a grandchild far beyond the perpetuities period. Modern reforms (USRAP wait-and-see, cy pres) salvage many of these, but the UBE tests common-law RAP unless told otherwise.

A class gift to grandchildren measured from a living grandparent, where the choice ignores the rule and calls the gift valid because the grandparent is elderly.

Charity-to-Charity Exception

When a fee simple determinable is given to one charity with a shifting executory interest in another charity ('to Charity A so long as used as a hospital, then to Charity B'), RAP does not apply to the executory interest. The exception is narrow: both takers must be charities. A shift from charity to private party, or from private party to charity, gets full RAP treatment.

An answer that voids Charity B's executory interest under RAP without first checking whether the prior taker is also a charity.

All-or-Nothing Class-Gift Rule

For a class gift to be RAP-valid, the interest must vest in ALL class members within the perpetuities period — not just one. If even one possible class member's interest might vest too remotely, the entire class gift fails. The rule of convenience (which closes a class when any member can demand distribution) is your common workaround on the exam.

A choice that upholds 'to A's children who reach 30' as valid for the children already over 30 — bar examiners want the entire gift voided.

Possibility of Reverter vs Right of Entry

Durational language ('so long as,' 'until,' 'while,' 'during') creates a fee simple determinable with an automatic possibility of reverter in the grantor. Conditional language ('but if,' 'provided that,' 'on condition that') creates a fee simple subject to condition subsequent with a right of entry that the grantor must affirmatively exercise. Both grantor interests are RAP-exempt, but they differ on whether possession reverts automatically or requires re-entry — and that controls statute-of-limitations questions.

A vignette using 'but if' language and an answer choice that calls the grantor's retained interest a possibility of reverter.

How it works

Approach every future-interest question in two passes. First, classify: identify the present estate, then ask who holds the future interest. If the grantor holds it, it is a reversion, possibility of reverter, or right of entry — none of those touch RAP. If a transferee holds it, decide whether it is a remainder (waits politely for the prior estate to end naturally) or an executory interest (cuts short the prior estate or springs out of the grantor). Then sub-classify the remainder as vested, vested subject to open, vested subject to complete divestment, or contingent. Second, run RAP only on contingent remainders, executory interests, and vested remainders subject to open. Picture the validating life: is there any human alive at creation whose death plus 21 years guarantees the interest will vest or definitively fail? If yes, it is good. If you can construct any far-fetched scenario — fertile octogenarians having more children, an unborn widow surviving 22 years, a measuring event that may occur centuries later — the interest is void from the start and you strike it from the conveyance.

Worked examples

Worked Example 1

Is the remainder to Diego's children who reach 30 valid under the common-law Rule Against Perpetuities?

  • A Yes, because Diego's two oldest children will necessarily reach 30, if at all, within Diego's lifetime plus 21 years.
  • B Yes, because the rule of convenience closes the class at Diego's death, validating the gift for any child then living.
  • C No, because Diego could have an additional child after the conveyance who might reach 30 more than 21 years after the death of every life in being at creation. ✓ Correct
  • D No, because the gift to Diego's children is a contingent remainder and contingent remainders are categorically void under the Rule Against Perpetuities.

Why C is correct: The remainder is a class gift contingent on reaching 30, so RAP applies and the all-or-nothing rule governs. Measured from 2015, any life in being (Diego, his then-living children) could die, and Diego could later father a child who would not reach 30 until more than 21 years after every measuring life had died. Because the interest might vest in even one class member beyond the period, the entire class gift is void at creation under the common-law Rule.

Why each wrong choice fails:

  • A: This focuses only on the two children alive at creation, but the all-or-nothing class-gift rule requires that the interest vest in EVERY potential class member within the period — including after-born children. The validity of the gift to the older children does not save the class. (All-or-Nothing Class-Gift Rule)
  • B: The rule of convenience closes a class when any member can demand distribution, but here distribution cannot be demanded until a child actually reaches 30, which may occur years after Diego's death. The rule of convenience does not save this gift. (All-or-Nothing Class-Gift Rule)
  • D: Contingent remainders are not categorically void; they are simply tested under RAP. A contingent remainder that must vest within a life in being plus 21 years is perfectly valid. This choice overstates the rule. (The Comma Test for Vested-vs-Contingent)
Worked Example 2

Who owns the future interest in Greenacre?

  • A Anjali, because the conveyance gave her a valid shifting executory interest that survived Theodore's death.
  • B Anjali, because both the Society and Anjali are charitable institutions, so the charity-to-charity exception saves her interest from RAP.
  • C Vikram, because Anjali's executory interest violates the Rule Against Perpetuities, and the resulting possibility of reverter passed to Vikram by devise. ✓ Correct
  • D The Riverbend Historical Society, because once the conveyance was made and Theodore died, no enforceable future interest remained in Greenacre.

Why C is correct: Anjali received a shifting executory interest following a fee simple determinable. Because the museum-use condition could be breached at any time in the indefinite future — long after Anjali and any other life in being have died plus 21 years — the executory interest violates common-law RAP and is void at creation. When the executory interest is struck, the durational language leaves the grantor with a possibility of reverter, which passed under Theodore's residuary clause to Vikram.

Why each wrong choice fails:

  • A: This treats the executory interest as RAP-valid, but a shifting executory interest tied to an open-ended use restriction can vest centuries later. The interest must be voided under the common-law Rule. (Fertile Octogenarian Trap)
  • B: The charity-to-charity exception requires both the prior taker AND the holder of the executory interest to be charities. Anjali is a private individual, so the exception does not apply. (Charity-to-Charity Exception)
  • D: Striking Anjali's interest does not give the Society a fee simple absolute. The durational 'so long as' language remains, leaving a possibility of reverter in the grantor that descends through Theodore's estate. (Possibility of Reverter vs Right of Entry)
Worked Example 3

How should Yolanda's and Felix's interests be characterized, and are they valid under the Rule Against Perpetuities?

  • A Yolanda holds a contingent remainder and Felix holds an alternative contingent remainder; both are valid because they must vest, if at all, at Marcus's death.
  • B Yolanda holds a vested remainder subject to complete divestment and Felix holds a shifting executory interest; both are valid because both interests must vest or fail at Marcus's death. ✓ Correct
  • C Yolanda holds a vested remainder subject to open and Felix holds a shifting executory interest; Felix's interest is void under the Rule Against Perpetuities.
  • D Yolanda holds an indefeasibly vested remainder and Felix holds nothing, because the divesting condition is repugnant to the prior fee.

Why B is correct: Yolanda is named, ascertained, and the gift to her is unconditional on its face — she has a vested remainder. The 'but if' clause is a separate divesting condition, so her interest is vested subject to complete divestment. Felix's interest cuts short Yolanda's vested estate, making it a shifting executory interest. Both interests must vest or fail at Marcus's death (a life in being), so RAP is satisfied.

Why each wrong choice fails:

  • A: This misclassifies Yolanda's interest. Because the condition appears in a separate clause after a clean gift to Yolanda, she has a vested remainder subject to complete divestment, not a contingent remainder. (The Comma Test for Vested-vs-Contingent)
  • C: Yolanda is a single named individual, not a class, so 'vested remainder subject to open' is the wrong category. And Felix's executory interest is RAP-valid because it must resolve at Marcus's death. (All-or-Nothing Class-Gift Rule)
  • D: Divesting conditions tied to a remainder are not repugnant to the prior estate; they are routinely enforced. This choice invents a doctrine that does not exist for these facts. (The Comma Test for Vested-vs-Contingent)

Memory aid

Classify with 'PEPSI': Possibility of reverter, Executory interest, Possession (reversion), Subject-to-condition (right of entry), Indefeasibly vested. For RAP, run 'CEO': Contingent remainders, Executory interests, Open class gifts — only these three test under the Rule. Then ask: 'Is there any life in being whose death + 21 years guarantees vesting?'

Key distinction

The line between a vested remainder subject to complete divestment and a contingent remainder turns on where the conditional language sits. If the condition is built into the gift itself ('to B if B reaches 25'), the remainder is contingent and RAP applies. If the gift is unconditional but later cut short by a separate clause ('to B, but if B dies before A, then to C'), B has a vested remainder subject to complete divestment (RAP-exempt) and C has a shifting executory interest (RAP-tested).

Summary

Classify the future interest first, then run RAP only on contingent remainders, executory interests, and vested remainders subject to open — voiding any interest that might vest beyond a life in being plus 21 years.

Practice future interests and the rule against perpetuities adaptively

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Frequently asked questions

What is future interests and the rule against perpetuities on the UBE?

A future interest is a presently existing property right that entitles the holder to possession (or a chance at possession) at some point in the future. Future interests are sorted first by who holds them — the grantor (reversion, possibility of reverter, right of entry) or a third-party transferee (remainder or executory interest) — and then by their qualities (vested, contingent, vested subject to open, vested subject to complete divestment). The common-law Rule Against Perpetuities (RAP) voids any contingent remainder, executory interest, or vested remainder subject to open if it might vest or fail to vest more than 21 years after the death of some life in being at the creation of the interest. RAP applies only to those three interest types; reversions, possibilities of reverter, rights of entry, and indefeasibly vested remainders are exempt.

How do I practice future interests and the rule against perpetuities questions?

The fastest way to improve on future interests and the rule against perpetuities is targeted, adaptive practice — working questions that focus on your specific weak spots within this sub-topic, getting immediate feedback, and revisiting items you missed on a spaced-repetition schedule. Neureto's adaptive engine does this automatically across the UBE; start a free 7-day trial to see your sub-topic mastery climb in real time.

What's the most important distinction to remember for future interests and the rule against perpetuities?

The line between a vested remainder subject to complete divestment and a contingent remainder turns on where the conditional language sits. If the condition is built into the gift itself ('to B if B reaches 25'), the remainder is contingent and RAP applies. If the gift is unconditional but later cut short by a separate clause ('to B, but if B dies before A, then to C'), B has a vested remainder subject to complete divestment (RAP-exempt) and C has a shifting executory interest (RAP-tested).

Is there a memory aid for future interests and the rule against perpetuities questions?

Classify with 'PEPSI': Possibility of reverter, Executory interest, Possession (reversion), Subject-to-condition (right of entry), Indefeasibly vested. For RAP, run 'CEO': Contingent remainders, Executory interests, Open class gifts — only these three test under the Rule. Then ask: 'Is there any life in being whose death + 21 years guarantees vesting?'

What's a common trap on future interests and the rule against perpetuities questions?

Running RAP on reversions or indefeasibly vested remainders

What's a common trap on future interests and the rule against perpetuities questions?

Forgetting class gifts must vest in all members within the period (all-or-nothing rule)

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