The $15 million trap in old estate plans

Most estate plans drafted before this year are quietly executing a document their authors never wrote, because the One Big Beautiful Bill Act, signed in July 2025, made the federal estate, gift, and generation-skipping transfer tax exemption permanently $15 million per individual and $30 million for a married couple, effective January 1, 2026. Eleven months into the first year those numbers actually govern, the year-end review season underway is the last comfortable window to catch what they broke.

The mechanical failure is almost banal in its simplicity. A document drafted in 2004 instructs the trustee to fund the family trust — the bypass or credit shelter trust — with the largest amount that can pass free of federal estate tax, then pour the balance into a marital trust for the surviving spouse; when the client signed it, that formula moved $1.5 million, and today it moves $15 million. Nothing in the document changed. The law did.

That arithmetic, ten times larger, does not scale gracefully: consider a couple with a $12 million estate, where the family trust now takes everything and the marital trust takes nothing. If the family trust is fully discretionary for the surviving spouse and the children, the result is awkward but workable; if the remainder beneficiaries are children from a first marriage and the survivor is a second spouse, the decedent has disinherited the very person the document was built to protect.

The damage concentrates in three provisions that advisors rarely re-read until a death triggers them: the marital and bypass funding formula, which in many documents will now sweep an entire estate into the wrong trust; the GST allocation language, which is moving far more into dynasty structures than any drafter contemplated; and the bypass trust itself, which now costs more in forfeited income tax basis than it ever saved in estate tax for a growing number of families. Documentation of all three tends to surface after the client has died, when no one is left to explain what the original intent was.

The GST exemption tracks the basic exclusion amount, so it sits at $15 million as well, and it still is not portable between spouses: if the first spouse to die fails to use it, that exemption is gone permanently. Formulas that carve out an amount equal to the settlor's remaining GST exemption for a dynasty trust are pushing far more into that structure than anyone planned when the numbers were fractions of today's.

Older documents also lean on the reverse qualified terminable interest property election, which treats the first spouse to die as the transferor for GST purposes and allows that spouse's exemption to be applied to a marital trust; that election works in tandem with inclusion ratio language, the fraction measuring how much of a trust is exposed to GST tax. Both were calibrated against the old exemption figures, and when the drafter wanted a zero inclusion ratio, that language now has to prove it still delivers one, because it will not survive a casual glance at the end of a marital formula review.

A bypass trust funded at today's exemption level locks assets in a structure whose beneficiaries forfeit the step-up in income tax basis that outright ownership or a marital trust would have secured at the surviving spouse's death, quietly eroding family wealth in ways that never appear on a tax return. At the old exemption levels the estate tax savings typically dwarfed that basis cost; at $15 million the equation flips for a materially larger set of families, where the estate tax bill may be zero either way but the income tax burden on the eventual sale of appreciated assets becomes real and avoidable.

This is precisely the kind of planning failure that masquerades as a successful outcome: no tax is due, no filing is flagged, and the family absorbs the cost as a quiet drag on what they eventually sell. The drafting intent to shelter the maximum from estate tax was honored perfectly; the economic intent was not.

The permanence of the $15 million figure is precisely what makes these clauses dangerous, because drafters who assumed future legislation would eventually lower the number, or that inflation adjustments would keep the exemption modest, built their formulas on an expectation of change; permanence removed the one force that would have contained the error.

The window for correction is limited: a client who dies with an outdated formula clause is not a planning failure that can be unwound but a dispositive outcome that stands, no matter how far it departs from intent. The cost of review is an afternoon of reading; the cost of inaction is a family conflict that surfaces years later, when the document's silence becomes the loudest voice in the room.

Advisors should treat this as a document-by-document audit, not a form-letter mailing. The three clauses interact; fixing the funding formula without re-examining the GST allocation language is how zero-inclusion-ratio problems get birthed. The bypass trust basis question, meanwhile, is a strategic decision about whether the trust should be funded at the full exemption when estate tax is no longer a live threat for the family's actual net worth, not a drafting matter at all.

For the planner, the uncomfortable reality is that the documents most at risk are the ones that have worked perfectly for twenty years: the 2004 trust that moved $1.5 million without incident was a good document, but the same document moving $15 million is a different instrument entirely, and it deserves to be read like one — before the family reads it for the first time at a funeral.

Practically, the review should start with the formula clause in trust documents, then trace the funding outcome against the family's actual wishes at current exemption levels, where a formula that was perfectly legal twenty years ago may no longer speak the client's intent in a world where the exemption is ten times larger than when the words were written.

Where documents allow, trustees and advisors should consider amending the funding formula to a fixed dollar amount or adding language that accounts for a surviving spouse's own exemption; where the documents are silent, a conversation with the client about whether the bypass trust still makes economic sense should precede any decision to fund it fully. The GST allocation needs its own look, and the reverse QTIP election needs to be stress-tested for the inclusion ratio it actually produces.

There is no deadline in the code that forces the issue, no notice from the IRS, no letter from the bank; the misfire happens inside a document that everyone assumed was settled, and year-end review season is the last moment the mistake is cheap to find. In January, it starts being expensive to miss.