When a grantor pays income tax on an IDGT's earnings, that payment is treated as a tax-free gift to the trust beneficiaries. On a $10 million trust earning 8% annually, that can represent $200,000 to $300,000 per year in additional, untaxed value transfer.
Dynasty Trust
A dynasty trust is built to last multiple generations, often 100 to 1,000 years depending on the state, making South Dakota, Nevada, and Delaware the preferred domiciles. Assets transferred in are shielded from estate tax at every generational handoff because the trust itself never terminates and never triggers a taxable transfer event. The grantor funds the trust using lifetime gift tax exemption (currently $13.61 million per individual in 2024) or generation-skipping transfer (GST) exemption, and once that exemption is allocated, growth inside the trust compounds permanently outside the taxable estate. If you want to understand how the GST exemption stacks on top of this structure, Dynasty Trust vs GST: How These Two Structures Actually Work Together walks through the mechanics in detail.
Intentionally Defective Grantor Trust (IDGT)
An IDGT is designed with a specific tax quirk: it is complete for gift and estate tax purposes (assets leave the grantor's estate) but incomplete for income tax purposes (the grantor still pays the trust's income tax personally). That income tax payment is itself a tax-free gift to the trust because the grantor covers the liability without it counting as an additional taxable transfer. The most powerful use is the installment sale to IDGT, where the grantor sells appreciating assets to the trust in exchange for a promissory note at the IRS applicable federal rate (AFR), currently in the 4-5% range, allowing the spread between AFR and actual asset returns to accumulate inside the trust gift-tax-free. Setup typically runs $5,000 to $15,000 in legal fees, and the strategy works best when the grantor has sufficient outside assets to keep paying the trust's income tax without straining personal cash flow.
Where They Overlap and Where They Split
Both structures remove future appreciation from the taxable estate the moment assets are transferred, and both can hold the same asset classes including real estate, private equity, S-corp shares with proper planning, and life insurance. The split is in duration and tax reporting. A dynasty trust is typically a non-grantor trust after the grantor's death, meaning it files its own tax return and pays its own tax at compressed trust rates (37% kicks in at just over $15,000 of taxable income in 2024). An IDGT is a grantor trust by definition, so the grantor absorbs all income tax, which is the feature, not a bug, but it does create ongoing cash demands. Many sophisticated planners fund a dynasty trust structure and layer an IDGT installment sale on top, using the IDGT note to move an initial lump of assets while gifting additional amounts into the long-duration trust over time.
Which Structure Fits Which Situation
Use an IDGT when you have a specific high-value, high-growth asset you want to freeze and transfer now, typically a business interest or concentrated equity position, and you have the income to absorb the trust's ongoing tax bill. Use a dynasty trust when the goal is permanent, multi-generational wealth preservation where the structure needs to outlive not just you but your children and grandchildren. For families with enough exemption and assets to deploy, the combination play is most common: an installment sale into an IDGT to move the asset efficiently, with the IDGT itself designed to convert into or pour over to a dynasty trust at the end of the note term.
Things people ask first.
Can an IDGT also be a dynasty trust?
Yes. The grantor trust status (IDGT) and the trust's duration (dynasty) are separate features. You can draft a trust to be intentionally defective for income tax purposes during the grantor's lifetime while also giving it a 1,000-year term in South Dakota. These two characteristics do not conflict.
What happens to the IDGT when the grantor dies?
At the grantor's death, the IDGT loses its grantor trust status and converts to a non-grantor trust. The trust then files its own tax return and pays tax at compressed trust rates. This can significantly increase the annual tax drag, which is why planners often build in provisions to toggle grantor trust status or distribute income to beneficiaries in lower brackets.
How much exemption do I need to fund a dynasty trust?
There is no legal minimum, but the structure only makes economic sense after accounting for setup costs of $5,000 to $20,000 plus annual trustee fees. Most planners target at least $1 million to $2 million in initial funding to make the overhead worthwhile. Families funding $5 million or more get the most dramatic compounding benefit over multiple generations.
Does an installment sale to an IDGT use up my gift tax exemption?
The sale itself does not if it is structured as a true arms-length installment sale at or above the AFR. However, planners typically seed the IDGT with an initial gift equal to roughly 10% of the sale price (the "seed gift") to give the trust economic substance, and that seed does consume exemption. The bulk of the transfer happens via the note, not the exemption.
Which states are best for a dynasty trust?
South Dakota, Nevada, and Delaware lead the pack. South Dakota allows trusts to last 1,000 years, has no state income tax on undistributed trust income, and has some of the strongest asset protection statutes. Nevada offers similar benefits with a 365-day fraudulent transfer lookback period. Delaware is the most established legally but is slightly less favorable on the duration and tax front.
What assets work best inside an IDGT installment sale?
Assets with high expected appreciation and a defensible current valuation work best, including closely held business interests, real estate, and family limited partnership interests. A discount on valuation (typically 15% to 35% for lack of marketability and control) can be applied at the time of the sale, further reducing the note size and the amount subject to interest.
Ready to pick the right structure and actually execute it?
The Offshore Playbook covers dynasty trust formation, IDGT installment sale mechanics, state selection, and the combination strategies that high-net-worth families use to eliminate estate tax across generations. Gramps.chat can answer your specific structure questions in real time.
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