Intentionally Defective Grantor Trust (IDGT): UHNW Estate Planning Guide

Not tax or legal advice. Verify all figures and strategies with qualified estate counsel before acting.

An Intentionally Defective Grantor Trust (IDGT) is the most widely used technique for transferring large illiquid assets — a closely-held business, real estate portfolio, or pre-IPO equity — out of a taxable estate without triggering capital gains or using significant gift-tax exemption. The structure is "defective" on purpose: complete for estate tax (the assets leave your estate) but incomplete for income tax (you still pay tax on trust earnings as if you owned them). That asymmetry is exactly what makes the strategy work.

The One Big Beautiful Bill Act (OBBBA, July 2025) permanently set the federal estate and gift exemption at $15M per person — creating a significant window for IDGT planning in 2026. Families with illiquid assets that have significant appreciation potential have an unusually strong case for acting now.¹

How an IDGT works: the estate/income split

The "defect" in an IDGT is a deliberate provision in the trust agreement that causes the IRS to treat the trust as owned by the grantor for income tax purposes — while the trust is simultaneously treated as a completed, irrevocable transfer for estate tax purposes.

The most common defect used in practice is the substitution power under IRC § 675(4): the grantor retains the right to reacquire trust assets by substituting other property of equivalent fair market value. The IRS confirmed in Rev. Rul. 2008-22 that this power, by itself, does not cause estate inclusion — so the assets leave your estate while you remain the owner for income tax.²

Other commonly used defects include:

• IRC § 677: Trust income may be used for benefit of the grantor's spouse without trustee approval.
• IRC § 675(2): Trustee can lend trust assets to grantor without adequate security (rarely used alone).

The result: all trust income, capital gains, and deductions flow through to your personal Form 1040 each year — as if the trust didn't exist for income tax. Meanwhile, trust assets (and all their future appreciation) are completely outside your taxable estate.

The installment sale: step by step

Most IDGTs are funded not by a gift, but by a sale. You sell assets to the trust in exchange for a promissory note equal to the asset's fair market value. Because the trust is your grantor trust for income tax, the IRS treats this as a sale to yourself — no capital gain is recognized. Rev. Rul. 85-13 confirmed this: a transaction between a grantor and their grantor trust is disregarded for income tax purposes.³

Step 1 — Seed the trust with a gift. Before the sale, gift a minimum of approximately 10% of the intended sale price to the trust in cash or marketable securities. This gives the trust the economic substance to take on the promissory note — without the seed gift, the IRS may challenge the transaction as a retained-interest arrangement (a "sale" where the grantor effectively kept everything). A $20M sale typically requires a $2M seed gift.⁴

Step 2 — Sell assets to the trust at fair market value. The sale must be at FMV, documented with a qualified appraisal for closely-held business interests, real estate, or other non-marketable assets. The trust issues a promissory note equal to the FMV of what it receives.

Step 3 — Set the note rate at or above the applicable federal rate (AFR). The interest rate on the note must equal at least the IRS-published AFR for the note's term as of the month the sale occurs.⁵

Compare this to the §7520 rate (5.00% for May 2026), which is the hurdle rate for GRATs. The AFR for a mid-term IDGT note (4.08%) is nearly a full percentage point below the §7520 GRAT hurdle — meaning the IDGT transfers wealth to heirs at a lower required return than a GRAT. For assets expected to return 8–12%, this difference compounds meaningfully over a 7–10 year note term.

Step 4 — Trust pays interest; grantor reports it as income. The trust makes annual (or more frequent) interest payments to you at the AFR rate. Because the trust is a grantor trust, you include those interest payments in income and effectively ignore them for income tax — the trust's assets grow at the full economic return, not the after-interest return.

Step 5 — Note matures; balloon payment redeems the note. At maturity, the trust pays you the principal balance (typically structured as an interest-only note with a balloon). The assets remain in the trust. All appreciation above the AFR accumulated inside the trust — outside your estate — for the full term.

The math: $20M business example

Suppose a 57-year-old founder holds a $20M closely-held business growing at 10% annually and wants to pass maximum value to the next generation using minimal gift-tax exemption.

Year 9 outcomes (business grows at 10%/year):

The $9M in estate tax savings came from a $2M exemption commitment — a 4.5:1 leverage ratio. That leverage is the defining feature of an IDGT vs. a direct gift, which uses $1 of exemption for every $1 transferred.

The grantor income tax feature

Because the IDGT is a grantor trust, you pay income taxes each year on all trust income — dividends, interest, rent, capital gains realized inside the trust. The trust itself pays nothing. This sounds like a burden, but it's actually an additional tax-free transfer to heirs.

Every dollar of income taxes you pay on trust earnings is a dollar the trust keeps compounding. If the trust earns $2M this year and would otherwise owe $900K in income tax (45% combined federal + state), the trust retains the full $2M while you pay the $900K from your personal funds. That $900K outflow from your estate effectively reduces your estate and increases the trust — without using any gift-tax exemption.

The IRS confirmed in Rev. Rul. 2004-64 that a grantor's payment of income taxes on behalf of a grantor trust is not a gift — even if the trust document gives the trustee discretion to reimburse the grantor, the mere existence of that power doesn't cause estate inclusion.⁶ Most IDGT drafters include a reimbursement power (giving the trustee discretion to reimburse, not an obligation) to preserve flexibility while keeping the income tax benefit.

The substitution power: basis planning

The § 675(4) substitution power — the same provision that creates grantor trust status — also gives you a valuable basis-planning tool. You can swap a high-basis asset you own personally into the trust in exchange for a low-basis trust asset. The low-basis asset then sits in your estate, where it will receive a § 1014 step-up in basis at death, eliminating the embedded capital gain for your heirs.

This swap must be done at fair market value — the substitution must be of "equivalent value" — and it should be documented carefully. But it means an IDGT funded with appreciated assets doesn't permanently sacrifice the step-up. You can re-arrange which assets sit inside vs. outside the estate as circumstances change, capturing the step-up on low-basis positions while keeping appreciating assets (which benefit more from escaping estate tax) in the trust.

This feature is not available with GRATs or SLATs — another structural reason IDGT is often the preferred vehicle for illiquid, low-basis assets.

IDGT vs GRAT vs SLAT

Practical sequencing guidance:

• Use an IDGT installment sale for large illiquid interests — the family business, a real estate portfolio, or pre-IPO equity — where you want to avoid using most of your $15M exemption and need the lower AFR hurdle (not the §7520 GRAT rate).
• Use a GRAT in parallel for publicly-traded concentrated positions or for rapid-appreciation events (pre-IPO, pre-acquisition close) where the §7520 hurdle is acceptable and the "free option" nature of a GRAT (failure is costless from a gift-tax perspective) is valuable.
• Use a SLAT for post-liquidity cash and diversified securities where you want to permanently use $15M of exemption and retain access through your spouse.
• The most effective UHNW estate plans typically use all three in combination: IDGT for the business, GRATs for public equity, SLAT for liquidity-event proceeds.

Best assets to sell to an IDGT

Strongest candidates:

• Closely-held business interests: The defining IDGT asset. Business interests often carry valuation discounts for lack of control (10–30%) and lack of marketability (10–30%), compounding on top of each other. Selling at a discounted FMV reduces the note amount — and therefore the exemption cost — while moving all future appreciation out of the estate. A $20M business valued at $14M with discounts produces a $14M note, not a $20M note.
• Real estate holdings: Rental portfolios, commercial property, land. Illiquidity discounts are available, and the future appreciation (especially in a 10–20 year horizon) can be substantial. Coordinates well with the asset protection structures (FLPs, LLCs) described on the asset protection page.
• Pre-IPO equity: Private company stock valued at the current 409A valuation, before an anticipated IPO or acquisition premium. The IDGT locks in today's (lower) valuation; all post-sale appreciation moves to heirs. Coordinate with the IPO financial planning timeline.
• Private equity fund LP interests: If the fund is in early J-curve and FMV is below cost, this may be the ideal moment to sell the LP interest to the IDGT. Requires GP consent for assignment.

Assets to approach carefully:

• Highly appreciated marketable securities: No capital gain on sale to the IDGT (grantor trust disregard). But if the trust later sells these securities, the gain flows to your personal return — make sure you have liquidity to cover the tax bill.
• S-corporation stock: Grantor trusts are qualified S-corp shareholders during the grantor's lifetime. After the grantor trust status terminates (at grantor's death), the trust must convert to a QSST or ESBT within 2 years or the S election terminates. Requires careful drafting.
• Assets where FMV is easily challenged: If the IRS disputes the sale price and determines you sold at below FMV, the underpayment is treated as a gift — using exemption and potentially creating gift tax. Use qualified independent appraisals.

Risks and failure modes

Grantor dies while the note is outstanding

If you die before the promissory note matures, the note itself — not the trust assets — is included in your estate at its remaining face value. The trust assets stay outside the estate. This is meaningfully better than a GRAT failure (which brings the entire asset back into the estate), but it does mean partial inclusion. Mitigation: consider a decreasing-balance note structure, or purchase life insurance outside the estate (in an ILIT) to cover potential estate tax on the outstanding note balance.

Trust fails to make note payments

If the trust lacks liquidity to make annual interest payments, it must sell trust assets to fund them. For an illiquid business interest, this can be operationally difficult. Solution: the business must generate sufficient distributions to cover the interest payments, or the trust retains liquid assets for this purpose. Model the cash flows carefully before structuring the note terms.

Grantor trust status terminates unexpectedly

If grantor trust status terminates during the note term (for example, the defect provision is invalidated by a court), the trust would become a separate taxpayer — and the outstanding note would become a third-party loan from the trust's perspective. Future trust income becomes taxable to the trust at compressed trust rates (37% above $16,550 in 2026). This is rare but should be anticipated in the trust document.

IRS valuation challenge

The most common attack point is the FMV at the time of sale. If the IRS determines the business or real estate was sold below FMV, the shortfall is treated as a taxable gift — using exemption and potentially triggering gift tax. A qualified appraisal from a credentialed appraiser (ASA or ABV designation) is essential. For businesses, the appraisal should be contemporaneous with the sale, not prepared after the fact.

Incomplete estate planning integration

An IDGT by itself doesn't address state estate taxes (several states have exemptions well below $15M), generation-skipping tax allocation, or the trust's investment strategy. Failure to allocate GST exemption to the trust at funding means distributions to grandchildren will be subject to the 40% GST tax — erasing a significant portion of the benefit. Coordinate IDGT planning with the full estate plan.

When an IDGT makes sense — and when it doesn't

IDGT installment sale typically makes sense when:

• You have a large illiquid asset (business, real estate, pre-IPO equity) expected to appreciate significantly over a 7–15 year horizon.
• You want to move the asset out of your estate with minimal gift-tax exemption use — the leverage ratio of an IDGT far exceeds a direct gift.
• The asset can generate (or you have outside liquidity to cover) annual AFR interest payments on the note.
• You want to retain the § 675(4) substitution power to manage basis planning at death.
• You're unmarried or prefer not to use a SLAT structure — IDGTs work equally well for single and married families.

IDGT may not make sense when:

• The asset has very low expected returns — if it barely clears the AFR hurdle, the trust transfers little wealth.
• Liquidity for annual note payments is tight — a strained note can create IRS scrutiny or force asset sales at unfavorable times.
• The FMV appraisal is contested or contentious — a successful IRS challenge converts a gift-tax-efficient transfer into a taxable gift.
• Your estate is below the combined exemption ($30M per couple) — if estate tax isn't actually a concern, the cost and complexity of an IDGT may not be justified.
• You're close to death — a grantor who dies while a large note is outstanding partially defeats the strategy. For older clients, a SLAT (no term structure) may be more appropriate.

Working with a UHNW advisor on IDGT planning

An IDGT requires genuine coordination across three professionals:

• Estate planning attorney: Drafts the trust document with the correct grantor trust defect, the § 675(4) substitution power, appropriate trustee provisions, and GST exemption allocation language. Must be experienced in IDGT drafting — this is not a form document.
• Qualified appraiser: Values the business interest or real estate at FMV with any applicable discounts for lack of control and marketability. The appraisal must be contemporaneous with the sale and prepared by a credentialed professional. This is the single most important document for surviving IRS scrutiny.
• CPA: Prepares the Form 709 gift tax return for the seed gift, ensures the annual note interest is properly reported, and coordinates the grantor trust income allocations with your personal return. Also tracks grantor trust status and prepares the trust's income tax reporting (Form 1041 filed as a grantor trust).

The fee-only financial advisor's role is portfolio integration: determining which assets to fund (considering basis, asset type, expected return, and liquidity), how the IDGT fits within the broader estate plan (alongside GRATs, SLATs, and charitable structures), and how to manage the note cash flow requirements from a portfolio standpoint. At $30M+, the IDGT is rarely a standalone move — it's one piece of a coordinated multi-structure estate plan that should be reviewed annually.

Sources

1. IRS — 2026 tax adjustments under OBBBA: federal estate and gift exemption $15,000,000 per individual, permanent with inflation indexing. Annual gift exclusion $19,000 per recipient. Values verified May 2026.
2. Rev. Rul. 2008-22 — IRS ruling confirming that a grantor's retained § 675(4) power to reacquire trust corpus by substituting property of equivalent fair market value does not cause estate inclusion under § 2036 or § 2038. Basis for treating § 675(4) as the preferred IDGT defect.
3. Rev. Rul. 85-13 — IRS ruling holding that a sale of property between a grantor and their grantor trust is disregarded for federal income tax purposes: no gain or loss recognized, no installment sale treatment under § 453 applies.
4. RSM US — "Sales to Intentionally Defective Grantor Trusts Explained": overview of seed gift requirement (~10% of sale value), promissory note structure, AFR compliance, and ongoing administration requirements.
5. Rev. Rul. 2026-9 — IRS applicable federal rates for May 2026: short-term AFR 3.82%, mid-term AFR 4.08%, long-term AFR 4.83% (annual compounding); § 7520 rate 5.00%. Used for IDGT promissory note minimum interest rates and GRAT hurdle comparison.
6. Rev. Rul. 2004-64 — IRS ruling that a grantor's payment of income tax on grantor trust income is not a gift to the trust, even where the trust document gives the trustee discretion (but not an obligation) to reimburse the grantor for those taxes. Preserves grantor income tax feature as a tax-free additional transfer.

Tax and estate law changes frequently. All AFR and §7520 rates reflect May 2026 (Rev. Rul. 2026-9). Estate and gift exemption reflects 2026 under OBBBA. Trust income tax bracket ($16,550 for 37% rate) reflects 2026 IRS inflation adjustments. Verify all figures and structure with qualified estate planning counsel before acting.