Engineers design circuits for systems that may never get built. Trust lawyers draft provisions for situations that may never arise. The credit shelter trust I write into a will is the cleanest example: drafted in full, wired into the document, carrying nothing. Most stay that way. I draft them anyway.
A credit shelter trust — sometimes called a bypass trust or family trust — catches assets at the first spouse’s death and shelters them from estate tax at the second. The surviving spouse can be a beneficiary, typically receiving income and principal for health, education, maintenance, and support, but does not own the assets outright. The assets work for her during her lifetime but bypass her estate when she dies, and the deceased spouse’s exemption gets used instead of evaporating.
The mechanism earns its keep in New York for two reasons.
First, New York has no portability. The federal estate tax lets a surviving spouse port the deceased spouse’s unused exemption — file Form 706, walk away with a combined $30 million shelter in 2026. New York offers no such courtesy. If the first spouse’s $7.35 million exemption is not used at death, it is gone.
Why isn’t the exemption used? Any money left to a spouse at death uses the unlimited marital deduction – joint assets, IRAs, apartments owned jointly. The exemption is lost because the unlimited marital deduction was used instead.
Second, the cliff. New York taxes the entire estate, from the first dollar, the moment it crosses 105% of the exemption — $7,717,500 in 2026. That makes the surviving spouse’s eventual estate the high-wire act: everything she inherits at the first death stacks onto her own assets. The credit shelter trust is what keeps the combined number below the cliff.
Without a credit shelter trust, a couple with combined assets above the New York exemption can lose a substantial portion of those assets to state estate tax at the second death — tax that the trust would have spared by using the first spouse’s exemption when it had to be used. That is the problem the CST solves.
Dormant By Default
Drafting the credit shelter language into the will doesn’t fund it. The provision sits in the document, fully drawn, but the assets that could feed it usually don’t. A couple’s joint checking, the house held as tenants by the entirety, the IRA naming the spouse as primary beneficiary, the life insurance with the spouse named — all of it passes to the surviving spouse by operation of law, outside the will, before the will is ever read. The credit shelter trust inside the will gets nothing.
For most couples, that’s the right outcome. A household comfortably under the federal $15 million and the New York $7.35 million does not need the credit shelter trust to do anything. Everything to the survivor is the cleanest plan — no probate, no disclaimer, no funding mechanics, no surviving spouse trying to make HEMS decisions in the year after a death.
So the wiring sits dormant. The credit shelter trust is in the document. The assets aren’t routed to it. That looks decorative. It isn’t. It’s deferred.
Why Hardwiring the Credit Shelter Trust into Wills isn’t Optimal
A credit shelter provision sitting in a will can’t fund itself until the will is probated. In New York that means waiting on Surrogate’s Court — nine months at minimum, and longer for almost any reason: real estate to sell, an out-of-state executor who needs to post bond, a distributee no one can locate, tax waivers in transit.
The bigger problem is that the disclaimer mechanism — the bridge that’s supposed to feed the credit shelter trust when assets pass outside the will —is not hooked up. The assets passing outside of a will that can be disclaimed are few.
Real property held jointly can be disclaimed. Whether titled as joint tenants with right of survivorship or as tenants by the entirety, the surviving spouse can renounce her deceased spouse’s half-interest within nine months under EPTL §2-1.11. Treas. Reg. §25.2518-2(c)(4) treats that half as a deemed transfer at death, and continuing to live in the house does not count as accepting it. The brownstone is the workhorse asset of joint-property disclaimer practice.
Joint bank and brokerage accounts cannot be disclaimed in New York. Under New York Banking Law §675, opening a joint account creates a presumption of an immediate, completed one-half gift to the co-tenant — the moiety rule. That conflicts with federal tax law, which treats joint bank accounts as incomplete gifts until withdrawal precisely because the depositor can unilaterally regain her contributions. The federal disclaimer regulation keys off that incomplete-gift characterization: the survivor can disclaim because the transfer at death is what created her interest. New York’s moiety presumption says the transfer happened at opening, which forecloses the disclaimer at the threshold. The joint brokerage account that funds the household is not a candidate for the credit shelter mechanism — full stop.
Retirement accounts and life insurance fall in the middle. The spouse named as primary beneficiary can disclaim — but one distribution from an inherited IRA is acceptance, and the contingent beneficiary on the form has to actually route to the credit shelter trust for any of it to land where we want it. For non-probate assets — IRAs, life insurance, brokerage TOD accounts — the beneficiary form is what controls. The spouse can disclaim, but the disclaimed share goes to the contingent beneficiary named on the form. If that contingent is the credit shelter trust under the will, success. If it is the kids, the New York exemption disappears. Beneficiary designations done wrong a decade ago can’t be undone after death.
Even when the disclaimer mechanism applies, it has problems. To disclaim into the credit shelter trust, the surviving spouse cannot have accepted the benefit of the asset in the meantime. Take one distribution from the IRA where she is named as primary beneficiary, and the option is gone. So the will-based plan asks the surviving spouse to do one of three things, all bad: disclaim within nine months while in mourning and leave an inherited brokerage account untouched until the will can be probated and the CST created a year later; use them and quietly forfeit the disclaimer; or use them, disclaim anyway, and let the IRS unwind it later with a tax bill attached. None of those is a planning strategy.
When You’d Plug It In
If the couple’s situation changes such that the New York estate tax becomes a real exposure – the threshold is $7.35 million and the cliff hits the entire estate at $7,717,500 — they can plug in without redrafting the Will. The simplest moves are paperwork: remove the spouse as primary beneficiary on the IRA or 401(k) and name the credit shelter trust under the will as primary or contingent; update life insurance forms the same way; split joint accounts into solo names so that each spouse’s share passes through her own will into her own credit shelter trust at first death. None of this requires new estate planning documents. The will already does the heavy lifting. The clients just decide whether, and when, to energize it.
That decision usually doesn’t happen at signing. It happens at the next review, after the brownstone has appreciated, or an inheritance occurred, or NYS lowered the exemption, or one spouse retired and the other’s IRA quietly tripled. The right time to plug in is the moment the numbers start to bite — not at 40 when no one knows where they’ll be at 85.
Why I Put the Wiring in a Will Even When I Don’t Expect It to Carry Current
When I put Credit Shelter Trust planning in a couple’s wills, I don’t expect them to use it. If I expect them to use it, I recommend a trust. So why bother?
The world keeps moving. The federal exemption was $675,000 in 2001 and $15 million in 2026, and one election could cut it in half again. New York’s number moves more quietly but it moves. Asset values move faster than either. The couple worth $4 million today can be worth $9 million after a decade of compounding, a rezoning, or an inheritance from a parent they were not expecting to lose. The will drafted at 55 must still work at 85.
The disclaimer is the backup, but only for some assets. If the couple never plugs in during life — never updates beneficiary forms, never splits the joint accounts — and circumstances at death make the credit shelter useful anyway, the surviving spouse can disclaim, at least some assets.
My Younger Clients Can Revaluate. I expect my younger clients to reevaluate every five years. At that point, maybe they change to a trust structure or engage in deliberate retitling before death.
Inclusion costs nothing. The drafting is template work, the document is two pages longer, and the provision sleeps quietly until something wakes it. Every other form of optionality in finance — options, derivatives, insurance — comes with a premium. The credit shelter trust in a will doesn’t. Free optionality is rare in any field.
Credit Shelter Trusts Fit Better in a Revocable Trust
A revocable living trust sidesteps all of the problems inherent in the will schemata. At first death the trust simply continues; the trustee allocates assets to the credit shelter share; funding happens privately, on the trustee’s schedule, with no docket number, sometimes no disclaimer even required, and no behavioral landmines. The surviving spouse keeps living her life. Most importantly, the language in the trust severs joint property – no need to do it in the real world.
This is why most of my clients with assets over $5 million dollars end up in trust-based plans. The credit shelter mechanism does its cleanest work there.
Good Circuitry Matters
A credit shelter trust in a will is not a prediction. It is wiring. Most of the time it carries no current, because the NYS exemption sits comfortably above the assets the couple is leaving directly to each other — and that’s exactly what I would recommend. Sometimes circumstances shift, and the clients come back to plug in. My CSTs sit quietly waiting in a will signed decades before.
I draft for the day the current may need to run.