GST Trust Definition: Exceptions, Exemption, and Allocation

A GST trust, as defined in Internal Revenue Code Section 2632(c), is any trust that could produce a generation-skipping transfer, unless it fits one of six specific exceptions written into the statute. The label matters because it triggers automatic allocation: if a trust meets this definition, the IRS automatically applies the transferor’s unused generation-skipping transfer tax exemption to gifts made into it. For 2026, that exemption is $15 million per person, and the tax it shields against runs at a flat 40%.¹²

The term catches many people off guard because it does not mean “any trust used for generation-skipping planning.” It is a narrow tax-code category. A trust can be built for a family’s grandchildren and still fall outside the definition; a trust primarily for a child can fall inside it. Whether the label attaches depends entirely on the six exceptions.

The Six Exceptions That Disqualify a Trust

The definition works by exclusion. A trust that could result in a generation-skipping transfer is a GST trust unless any one of the following is true.³

The trust requires that more than 25% of its assets be distributed to, or be withdrawable by, a non-skip person before that person turns 46.
The trust requires that more than 25% of its assets be distributed to a non-skip person who is living at the death of another individual identified in the instrument who is more than 10 years older than that non-skip person.
If a non-skip person dies before a specified date or event, more than 25% of the trust either passes to that person’s estate or is subject to a general power of appointment they hold.
Any portion of the trust would be includible in the gross estate of a non-skip person (other than the transferor) if that person died immediately after the transfer.
The trust is a charitable lead annuity trust, a charitable remainder annuity trust, or a charitable remainder unitrust.
The trust qualifies for a charitable deduction for annual unitrust payments and must pay principal to a non-skip person when those payments end.

For purposes of running this checklist, the statute assumes that any power of appointment held by a non-skip person will not be exercised. If none of the six exceptions apply, the trust is a GST trust, and automatic allocation kicks in on every transfer into it.³

Why the GST Trust Label Matters

Falling inside or outside the definition changes what the IRS does with your exemption by default. For direct skips, the tax code automatically allocates enough of the transferor’s unused GST exemption to cover the transfer unless the transferor opts out. For indirect skips, meaning transfers to a GST trust that are not themselves direct skips, the code also automatically allocates enough exemption to bring the trust’s inclusion ratio to zero.³

This is a safety net and a trap in the same rule. The safety net: exemption gets applied even if the transferor never filed a return or never thought about GST planning, and future distributions to grandchildren pass tax-free. The trap: for a family making annual exclusion gifts year after year to a Crummey trust that happens to satisfy the GST trust definition, automatic allocation quietly consumes exemption on gifts that were never intended to skip generations. Hundreds of thousands of dollars of exemption can drain away before anyone notices.

Electing Out of Automatic Allocation

A transferor who does not want automatic allocation to apply must say so. For direct skips, the election-out is made by describing the transfer on a timely filed Form 709 and stating that automatic allocation should not apply; paying the GST tax shown on the return also prevents automatic allocation.⁴

For indirect skips, opting out requires attaching a statement to Form 709 that identifies the trust and states specifically that the transferor is electing out for the described transfers. The statement must be attached to a return filed by the due date for the calendar year of the first covered transfer. A transferor can also block automatic allocation by affirmatively allocating a smaller amount of exemption than the value transferred, which tells the IRS that a mixed inclusion ratio is intentional.⁴

The Exemption Being Allocated

Each individual has a lifetime GST exemption equal to the basic exclusion amount for estate and gift taxes.⁵ For 2026, that amount is $15 million per person, $30 million for a married couple. The figure was set permanently by the One, Big, Beautiful Bill Act signed in July 2025 and will be indexed for inflation beginning in 2027.²

One feature of the GST exemption sets it apart from the estate and gift tax exemption. It is not portable. If your spouse dies without using their $15 million of GST exemption, that amount is gone; you cannot elect to use a deceased spouse’s unused GST exemption on your own transfers. Both spouses need to use their GST exemptions during life or at death, because portability will not clean it up later.

The Inclusion Ratio

How much of a trust is actually shielded is measured by the inclusion ratio. The ratio equals one minus the applicable fraction. The applicable fraction has the exemption allocated to the trust in the numerator, and the value of the property transferred into the trust (reduced by any recovered estate tax and any charitable deductions) in the denominator.⁶

Allocate $5 million of exemption to a $5 million transfer and the ratio is zero. The trust is fully exempt, and every future distribution, termination, and dollar of appreciation escapes the 40% tax. Allocate only $2.5 million to a $5 million transfer and the ratio is 0.5, meaning half of every future taxable event gets taxed at 40%. Planners aim for a zero inclusion ratio, and where that is not possible, they generally split the trust rather than live with a mixed ratio.

Structural Features That Keep a GST Trust Exempt

Getting the arithmetic right is only part of it. The trust itself has to be structured so the allocation actually takes effect and holds up over time.

Irrevocability and the ETIP

The trust must be irrevocable. If the transferor holds any power or interest that would pull the trust property back into their gross estate, the exemption allocation is suspended until that exposure ends. This suspension period is the Estate Tax Inclusion Period, or ETIP, and it runs from the date of transfer until the earlier of a generation-skipping transfer involving the property or the transferor’s death.⁷ Any attempted allocation during the ETIP simply does not take effect. Exemption locks in only after the transferor has truly let go.

Crummey Powers and the Five-and-Five Rule

Many GST trusts include Crummey withdrawal powers so that gifts qualify for the $19,000 annual gift tax exclusion.² A Crummey power gives each beneficiary a limited window, usually 30 to 60 days, to withdraw their share of a contribution. When a beneficiary lets that window lapse, the lapse can be treated as a transfer by the beneficiary, which could make the beneficiary a new transferor for GST purposes and blow up the trust’s inclusion ratio.

The five-and-five rule contains this risk. A lapse is not treated as a taxable release to the extent it does not exceed the greater of $5,000 or 5% of the trust’s assets at the time.⁸ For smaller trusts, withdrawal rights should stay within that safe harbor. Drafting Crummey powers above it without additional protective language is one of the most common failure points in GST planning.

Trust Duration

The longer the trust lasts, the more value the exemption protects. States vary in how long they let a trust run. Most historically enforced a Rule Against Perpetuities, but many have repealed or extended it, allowing trust terms anywhere from 360 years to indefinitely. A GST trust intended to leverage the exemption across multiple generations is generally established under the laws of a state that permits long-duration or perpetual trusts. These vehicles are often called dynasty trusts.

Filing the Allocation

Allocations are reported on Form 709, the United States Gift and Generation-Skipping Transfer Tax Return. The return is due April 15 of the year following the gift, so gifts made in 2026 are reported by April 15, 2027.⁹ If the donor dies during the year of the gift, the executor files by the earlier of the estate tax return deadline or April 15 of the following year.

Missing the return, or filing it without allocating exemption correctly, is where most GST planning falls apart. A missed or late allocation can mean the trust never reaches a zero inclusion ratio, and every future distribution and every dollar of appreciation stays exposed to the 40% tax. For trusts that satisfy the Section 2632(c) definition, automatic allocation provides a backstop. But relying on the backstop without checking the outcome is risky, particularly for families running multiple trusts or making transfers over many years. The definition determines whether automatic allocation applies at all; the return determines whether it applied the way you wanted.

1
Tax Policy Center. How Do the Estate, Gift, and Generation-Skipping Transfer Taxes Work
2
Internal Revenue Service. What’s New — Estate and Gift Tax
3
Office of the Law Revision Counsel. 26 U.S.C. 2632 – Special Rules for Allocation of GST Exemption
4
eCFR. 26 CFR 26.2632-1 – Allocation of GST Exemption
5
Office of the Law Revision Counsel. 26 U.S.C. 2631 – GST Exemption
6
Office of the Law Revision Counsel. 26 U.S.C. 2642 – Inclusion Ratio
7
Legal Information Institute. 26 U.S.C. 2642(f)(3) – Estate Tax Inclusion Period
8
GovInfo. 26 U.S.C. 2041 – Powers of Appointment
9
Internal Revenue Service. Instructions for Form 709