The Estate Tax Rule That Lets You Leave Your Spouse Unlimited Wealth Tax-Free

Federal estate tax law lets a married person leave any amount to a surviving spouse with no federal estate tax due at the first death. The rule is 26 U.S.C. § 2056(a). It lets an estate deduct the value of any property interest that passes from the deceased person to the surviving spouse, as long as that interest is included in the gross estate, and the statute puts no dollar cap on it. The timing matters because the IRS announced a bigger estate and gift tax exemption for 2027 today. Estates of deceased person who die during 2027 get a basic exclusion amount of $15,480,000, up from $15,000,000 for estates of decedents who died in 2026. How a couple handles the marital deduction decides whether they end up using one of those exclusions or both.

How the Deduction Delays the Tax Bill

The marital deduction pushes the estate tax back to the second death. Whatever the survivor inherits and still owns at death counts in the survivor’s own gross estate. The deduction removes assets from the first estate and adds them to the second.

IRS Statistics of Income data shows how big this area of tax is. In 2024, 7195 estate tax returns were filed, reporting $248944039000 in gross estates. Only 2663 of those returns owed net estate tax, and together they paid $23313220000. Estates of $50 million or more accounted for $15845602000 of that tax.

Which Transfers Qualify for the Deduction

• Property passing to the spouse: This covers legacies, jointly owned property, beneficiary designations and similar transfers, as long as the property is included in the gross estate.
• Terminable interests: These generally fail. Under § 2056(b)(1), an interest that ends when time runs out or when some event happens gets no deduction if someone else can take the property later.
• Citizen spouse: If the survivor is not a U.S. citizen, § 2056(d)(1)(A) bars the deduction. Exceptions apply.

Noncitizen Spouses Lose the Deduction Without a QDOT

Under § 2056(d)(2)(A), the deduction comes back for property passing to a qualified domestic trust (QDOT). § 2056A(a)(1) sets two rules for the trust. At least one trustee must be a U.S. citizen or a domestic corporation, and that trustee must have the right to withhold tax from any distribution other than income. The executor also has to elect QDOT treatment under § 2056A(a)(3).

The QDOT keeps the deferred tax alive. § 2056A(b)(1) levies estate tax on principal paid out while the survivor is alive and on whatever is left in the trust when the survivor dies. Treasury regulations add more rules for QDOTs holding more than $2 million: the trust must use a bank trustee, a bond, or a letter of credit equal to 65% of the trust’s value (26 CFR 20.2056A-2(d)(1)(i)). Under § 2056(d)(4), no QDOT is needed if the surviving spouse was a U.S. resident and becomes a citizen before the estate tax return is filed. Lifetime gifts can also move assets ahead of time: the annual exclusion for gifts to a noncitizen spouse is $194,000 for calendar year 2026 and $201,000 for calendar year 2027.

QTIP Trusts Let a Blended Family Split Control

A qualified terminable interest property (QTIP) trust gets around the terminable interest rule. Under § 2056(b)(7)(B)(ii), the spouse must receive all of the trust’s income at least once a year, and no one can appoint the property to anyone other than the spouse while the spouse is alive. Within those limits, the first spouse chooses who gets the remainder, such as children from a prior marriage. The executor makes the election on the estate tax return, and once made it cannot be reversed (§ 2056(b)(7)(B)(v)). The election can also cover just a specific portion of the trust (§ 2056(b)(7)(B)(iv)). The cost is that QTIP property is included in the survivor’s gross estate under § 2044(a).

Worked Example: How Leaving Everything Outright Can Cost $6 Million

A hypothetical founder dies in 2026 with a $40 million estate and leaves all of it directly to a spouse. The marital deduction covers the full amount, so no federal estate tax is due, and the founder’s $15,000,000 exclusion goes unused. To keep the math simple, assume the survivor also dies in 2026 with the same $40 million, no other assets, and no other deductions. Above the exclusion, the tax rate is effectively the 40% top rate in § 2001(c).

• No portability election: The survivor shelters only $15,000,000, so the estate tax is $10,000,000.
• Portability elected: Under § 2010(c)(2), the survivor’s exclusion is their own basic exclusion plus the deceased spouse’s unused amount. That totals $30,000,000, so the tax is $4,000,000.

The gap of $6,000,000 comes down to one filing.

Mistakes That Waste the First Spouse’s Exclusion

• Not filing because no tax is due: Portability is only available if the executor files a timely estate tax return and elects it there. A late return cannot carry the election, and the election cannot be undone (§ 2010(c)(5)(A)).
• Ignoring asset growth: The transferred amount is fixed at the first death. Any growth after that is taxed in the survivor’s estate. A credit shelter trust funded at the first death keeps that growth out of the survivor’s estate.
• Funding a QDOT too late: Property passing to a noncitizen spouse qualifies only if it is moved into a QDOT, or permanently assigned to one, before the estate tax return is filed (§ 2056(d)(2)(B)).

Questions That Decide Which Structure Fits

Four questions shape the choice: Is the combined estate likely to exceed the survivor’s exclusion? Is the survivor a U.S. citizen? Are there children from a prior marriage? Are the main assets ones that could grow fast, such as concentrated stock or a closely held business?

Leaving everything directly and relying on portability works poorly for blended families that want to control where the money ends up, for couples with fast-growing assets, and for noncitizen spouses. Plans built around trusts work poorly for couples well below the exclusion who value simplicity, and for survivors who need full control of the money.

Whichever structure fits, the paperwork around it is what trips most families up: a stale beneficiary form, an untitled account, a trust that was written but never funded. We put the full cleanup checklist in a free estate guide, here.

The $15,480,000 figure applies only to deaths in 2027. Any couple’s plan should be checked against the exclusion for the year of each death.

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