GST Tax: $13.99M Federal Exemption Planning at $20M Estates

The Generation-Skipping Transfer Tax (GSTT) is the third federal transfer tax in the IRC, alongside the estate tax (IRC §2001) and the gift tax (IRC §2501). It is the tax most likely to surprise high-asset families — not because it is hidden, but because the automatic allocation rules under IRC §2632 frequently misfire, and the planning machinery to use the $13.99M exemption efficiently requires affirmative action on the federal Form 706 or Form 709 that is often missed.

The GSTT was enacted in 1976 (rewritten in 1986) to prevent families from using multi-generation trust structures to avoid the estate tax at every intervening generation. Before GSTT, a $100M family fortune held in a long-term trust could pay estate tax at the founder's death, then pass to grandchildren, great-grandchildren, and remote descendants without further transfer tax for centuries. The GSTT closed that loophole by imposing a separate 40% flat tax on every transfer that skipped a generation.

The basic GSTT structure

GSTT applies to three categories of transfers under IRC §2611:

• Direct skips: outright transfers to skip persons. Example: a grandparent gifts $25K cash directly to a grandchild.
• Taxable terminations: a trust interest of a non-skip person terminates, leaving only skip persons as beneficiaries. Example: a trust pays income to the transferor's child for life; at the child's death the trust continues for grandchildren.
• Taxable distributions: a trust makes a distribution to a skip person while non-skip persons also have interests. Example: a multi-beneficiary trust where children and grandchildren are both beneficiaries distributes principal to a grandchild.

A "skip person" under IRC §2613 is either (a) a natural person two or more generations below the transferor (typically grandchildren or more remote descendants), or (b) a trust where all interests are held by skip persons. The 37.5-year rule under IRC §2651(d) generally treats unrelated persons more than 37.5 years younger than the transferor as skip persons.

The GSTT rate is a flat 40% under IRC §2641, identical to the top federal estate tax rate. Unlike the estate tax, there is no graduated bracket structure — every dollar of GSTT-able transfer above the exemption is taxed at 40%.

The 2026 GST exemption: $13.99M per individual

IRC §2631 sets the GST exemption at the same level as the federal estate tax exemption: $13.99M per individual for 2026, indexed annually under Rev. Proc. 2025-32. A married couple has $27.98M of combined GST exemption.

Critically, GST exemption is not portable between spouses in the way estate exemption is portable. The federal estate exemption allows the surviving spouse to claim the deceased spouse's unused exclusion (DSUE) under IRC §2010(c)(4). No equivalent rule applies to GST exemption. If the first spouse to die has $13.99M of unused GST exemption and it is not affirmatively allocated to a GST-exempt trust at the first death (via Form 706 Schedule R), the unused amount is forfeit forever. This is the single most expensive planning failure for $14M+ estates.

The inclusion ratio: the heart of the GST calculation

IRC §2642 sets up the "inclusion ratio" mechanism that determines how much GSTT a particular transfer or trust owes. The inclusion ratio is calculated as:

Inclusion ratio = 1 − (GST exemption allocated / Value at allocation)

A trust fully covered by GST exemption has inclusion ratio = 0 (zero), meaning 0% of distributions trigger GSTT. A trust with zero GST exemption allocated has inclusion ratio = 1.0, meaning 100% of distributions to skip persons trigger 40% GSTT. Partial allocation produces a fractional inclusion ratio.

Example: a $20M trust receives $13.99M of GST exemption allocation. Inclusion ratio = 1 − ($13.99M / $20M) = 1 − 0.6995 = 0.3005. A subsequent $1M distribution to a grandchild triggers GSTT on $1M × 30.05% = $300,500 at 40% = $120,200 GSTT. The same distribution on a full-exemption trust (inclusion ratio 0) would owe $0.

The inclusion ratio is locked at the time of GST exemption allocation. A trust that starts with inclusion ratio 0 stays at 0 forever, even as the trust assets grow from $13.99M to $50M to $200M over generations. This is the magic of dynasty trust planning — the GST exemption allocated at the start permanently shelters all future growth.

Worked example: $20M estate planning grandchildren bequests

Robert, a Houston resident, has a $20M estate. He wants to leave $6M to his three grandchildren ($2M each), $4M to his daughter, $5M to his son, $3M to his deceased son's widow (his daughter-in-law), and $2M to charity. He has used $0 of his federal estate exemption during his lifetime.

Robert is married to Elizabeth, who has a $5M estate of her own. The combined federal estate exemption available is $13.99M + $13.99M = $27.98M with proper portability election. The combined GST exemption is $13.99M + $13.99M = $27.98M with proper allocation by each spouse.

Scenario A — No GST allocation, direct outright bequests

• Gross estate: $20M
• Charitable deduction: ($2M)
• Marital deduction (none if married couple structure): $0 simplified
• Net taxable estate: $18M
• Federal estate exemption: ($13.99M)
• Federal taxable: $4.01M × 40% = $1.604M federal estate tax
• Direct skip to grandchildren: $6M (not in trust)
• GST tax: $6M × 40% = $2.4M (with no exemption allocation, full GST applies)
• Total federal transfer tax: $4.004M

Effective combined federal rate on the $6M to grandchildren: ($1.604M × 6/18 + $2.4M) / $6M = approximately 49%. The grandchildren receive $3.06M out of the $6M Robert intended for them.

Scenario B — Full GST exemption allocation to grandchildren bequests

Robert affirmatively allocates $6M of his $13.99M GST exemption to the direct skip transfers to grandchildren on his Form 706 Schedule R. The grandchildren-bound $6M becomes GST-exempt (inclusion ratio 0).

• Gross estate: $20M
• Charitable deduction: ($2M)
• Net taxable estate: $18M
• Federal estate exemption: ($13.99M)
• Federal taxable: $4.01M × 40% = $1.604M federal estate tax
• GST tax on direct skips: $0 (fully sheltered by allocated exemption)
• Total federal transfer tax: $1.604M

GST allocation saved Robert's family $2.4M in transfer tax. The grandchildren now receive nearly all of their $6M bequest. The remaining $7.99M of Robert's GST exemption is unused but irretrievable — once he dies, it cannot be carried over to Elizabeth's estate.

Scenario C — Dynasty trust funded with full $13.99M GST exemption

Instead of outright bequests to grandchildren, Robert directs $13.99M into a dynasty trust at his death, with children as current beneficiaries and grandchildren/great-grandchildren as remainder beneficiaries. He allocates his full $13.99M GST exemption to the dynasty trust (inclusion ratio 0).

• Federal estate exemption: covers $13.99M to dynasty trust + $0 of other
• Federal estate tax: on the remaining $4.01M taxable (same as scenarios A and B): $1.604M
• GST tax: $0 on dynasty trust (inclusion ratio 0)
• Dynasty trust grows from $13.99M at funding to (assuming 6% real net return) approximately $44M in 20 years and $140M in 40 years — all without further federal transfer tax through all generations.

The dynasty trust scenario produces the same year-one federal tax bill as Scenario B but compounds GST-tax-free across multiple generations. For families with multi-generation wealth, the dynasty trust is the structural conclusion of proper GST planning.

Automatic allocation of GST exemption: when it helps, when it hurts

IRC §2632 establishes automatic allocation rules that apply absent affirmative election:

• Direct skips (lifetime gifts): automatic allocation under IRC §2632(b). GST exemption is automatically allocated to a direct skip (e.g., a $19K annual exclusion gift to a grandchild) unless the transferor elects out on Form 709. This often helps — the allocation makes the grandchild gift GST-exempt.
• Indirect skips (gifts to GST trusts): automatic allocation under IRC §2632(c). GST exemption is automatically allocated to gifts to "GST trusts" (defined under §2632(c)(3)) unless the transferor elects out. This often hurts — routine annual exclusion gifts to a child's 529 plan or a family trust can inadvertently consume GST exemption needed elsewhere.
• Death-time allocation: if any GST exemption remains unallocated at the transferor's death, IRC §2632(c)(2) automatically allocates the remainder to taxable distributions and direct skips first, then to GST trusts in a specified ordering. This default allocation rarely matches the optimal allocation for the estate.

The practical implication: high-asset families must actively manage GST exemption every year, not just at death. A $19K annual exclusion gift to a 529 plan can consume $19K of GST exemption automatically if the 529 is treated as a GST trust under the technical definition. Over 20 years of routine gifting, that's $400K-$1M of GST exemption silently consumed without planning intent.

Affirmative election: opt-in and opt-out on Form 709

Form 709 (federal gift tax return) provides three GST elections:

• Affirmative allocation: allocate GST exemption to a specific transfer.
• Opt-out of automatic allocation: for direct skips or indirect skips where the transferor does not want exemption consumed.
• Election to treat trust as a GST trust (or not): for borderline trusts, the transferor can elect treatment.

High-asset families should file Form 709 annually for any year with gifts over the $19K annual exclusion, even if no gift tax is owed. The 709 filing creates a permanent record of GST allocation elections and prevents disputes years later about which exemption was used when.

Late allocation: the partial fix

If a transferor failed to make timely GST allocation in a prior gift year, IRC §2642(b)(3) allows late allocation on a subsequent Form 709 — but only at the trust's value at the date of late allocation, not at the original gift value. A trust funded with $1M five years ago that has grown to $1.6M would require $1.6M of GST exemption to fully shelter at late allocation. The late allocation feature is useful for partial fixes but never produces as good a result as timely allocation at the original transfer.

Treasury Regulation §26.2642-7 also provides a discretionary late allocation procedure (the "9100 relief" pathway) that allows extension of time to make GST elections when the failure to timely allocate was due to reasonable cause and not willful neglect. This is the standard fix for forgotten GST allocations discovered years later by a successor estate planner reviewing prior gift returns.

State-level GST tax: rare but exists

Most states do not impose their own GST tax. Of the 12 states (plus DC) with state estate taxes, only Connecticut has historically imposed a separate state-level GST tax (Connecticut repealed its state GST tax in 2019, leaving only the state estate tax in effect). Hawaii's estate tax statute under HRS Chapter 236E does not include a separate GST component.

For dynasty trust planning, state choice matters less for GST tax purposes than for state income tax purposes. A South Dakota or Nevada dynasty trust funded by a New York grantor still owes federal GSTT if not properly exempted, but the trust's income earned thereafter is generally not subject to state income tax. Most dynasty trusts are sited in states without rule against perpetuities — South Dakota, Nevada, Delaware, Alaska, Wyoming — for the combination of long-duration tax-free compounding plus favorable state income tax treatment.

GST and TCJA sunset risk

The GST exemption is unified with the federal estate exemption at $13.99M for 2026. Under the original TCJA structure, the exemption was scheduled to revert to approximately $7M (inflation-indexed) after the start of the 2026 tax year. OBBBA (2025) extended TCJA permanently, so as of the current verification, the $13.99M GST exemption is permanent rather than sunset-vulnerable.

The planning implication for families with $14M-$28M estates: the urgency that drove the SLAT/GRAT/dynasty trust building boom in 2024-2025 has eased, but the underlying tools remain available and economically valuable. For families approaching the federal threshold, locking in $13.99M of GST exemption through a dynasty trust at current asset values (and current exemption levels) protects against future legislative reversal. Even with OBBBA extension, future Congress can re-amend transfer tax law — the current exemption levels are not constitutionally protected.

Dynasty trust mechanics: state selection

A GST-exempt dynasty trust's ability to compound across many generations depends on state-level rule against perpetuities. The traditional common-law rule limits trust duration to "lives in being plus 21 years" — effectively 70-90 years. States that have abolished or extended this rule allow much longer dynasty trusts:

South Dakota and Nevada dominate the dynasty trust market because they combine perpetual duration with zero state income tax on undistributed trust income. A $13.99M dynasty trust earning 6% net real returns and compounding for 200 years without distributions reaches over $5 billion of value at the end of the period — all federal-transfer-tax-free for the 200-year duration. The state income tax savings on undistributed earnings also matter: avoiding 6-13% state income tax annually on the trust's earnings produces material additional compounding.

Common GST planning mistakes

• Failing to file Form 709 annually: high-asset families gifting through annual exclusions, 529 plans, and trust contributions need annual Form 709 filings to document GST elections, even when no gift tax is owed.
• Forgetting to allocate GST exemption at first death: the first spouse's $13.99M GST exemption must be actively allocated on Form 706 Schedule R or it is forfeit forever (no portability for GST).
• Letting automatic allocation consume exemption inadvertently: indirect-skip gifts to 529 plans and family trusts can silently use GST exemption needed elsewhere. Opt out via Form 709 election where appropriate.
• Treating GRAT remainders without GST planning: a GRAT's remainder typically has a much higher value than the front-end annuity. Allocating GST exemption to the GRAT remainder is technical — the allocation can't be made until the annuity term ends, so the value at allocation may be 5-10× the original GRAT funding amount.
• Ignoring the predeceased parent rule: if a transferor's child has died, the grandchildren of that child are not skip persons under IRC §2651(e). Failing to claim this rule on Form 706 can cause GSTT to be owed unnecessarily.
• Underestimating the value of multi-generation compounding: a $13.99M dynasty trust compounding at 6% real for 60 years reaches $390M at the end of the period. The GST shelter on that $390M is worth roughly $150M in federal transfer tax (assuming 40% combined estate+GST rate without the dynasty structure).

Decision framework: who needs GST planning?

1. Estates under $13.99M single / $27.98M couple: federal estate exemption fully covers; GSTT generally not a concern unless leaving substantial assets directly to grandchildren or in long-term trusts. Annual exclusion gifts to grandchildren still need GST allocation tracking.
2. Estates $14M-$28M: active GST allocation planning is essential. Affirmative allocation on Form 709 and Form 706. Consider lifetime gifting to dynasty trusts to use exemption while spouse alive.
3. Estates $28M-$100M+: dynasty trust structure is the standard solution. Full GST exemption ($27.98M for couple) allocated to dynasty trust; remaining estate planning around the trust structure.
4. Multi-generation wealth families ($50M+): nested dynasty trust structures, decanting mechanics, and trust-to-trust transfers to maximize multi-generational GST-tax-free compounding.

Key takeaways

• The Generation-Skipping Transfer Tax under IRC 2601-2654 is a 40% flat federal tax on transfers to grandchildren or unrelated persons more than 37.5 years younger than the transferor. It is in addition to any estate or gift tax on the same transfer.
• The 2026 GST exemption is $13.99M per individual, identical to the federal estate exemption, indexed annually. Married couples have $27.98M of combined GST exemption.
• GST exemption is NOT portable between spouses (unlike estate exemption). The first spouse's $13.99M of unused GST exemption is forfeit forever if not affirmatively allocated at first death on Form 706 Schedule R.
• Direct skips trigger automatic GST allocation under IRC 2632(b); indirect skips (gifts to GST trusts) trigger automatic allocation under IRC 2632(c). Both can be opted out of via Form 709 election.
• The inclusion ratio under IRC 2642 determines what fraction of a trust's distributions trigger GSTT. A trust with inclusion ratio 0 is permanently GST-exempt; the ratio is locked at the time of exemption allocation.
• Dynasty trusts in South Dakota, Nevada, Delaware, or Alaska compound GST-tax-free across multiple generations. A $13.99M dynasty trust at 6% real net returns reaches $44M in 20 years and $140M in 40 years — all without further federal transfer tax.
• On a $20M estate gifting $6M to grandchildren outright, proper GST exemption allocation saves $2.4M in federal transfer tax. Without allocation, the effective combined federal rate on the grandchildren bequest exceeds 49%.
• The predeceased parent rule under IRC 2651(e) treats grandchildren whose parent has died as the transferor's direct children (not skip persons), eliminating GSTT on those bequests automatically.