A Widow Can Inherit Her Husband’s Unused $15 Million Estate-Tax Exemption, Doubling Her Own, but Only If She Files a Form Almost No One Tells Her About

If your spouse died and their estate was nowhere near the federal estate tax threshold, you probably filed nothing with the IRS. That silence may have quietly cost your heirs millions. A surviving spouse can inherit the deceased spouse’s unused federal estate tax exemption, called the DSUE (Deceased Spousal Unused Exclusion), and stack it on top of her own, but only if the estate files IRS Form 706 to make the election. No form, no transfer. The exemption evaporates.

The Buried Benefit: Portability

Here’s the rule the funeral director, the bank, and often the family lawyer forget to mention. When one spouse dies, whatever chunk of the federal estate and gift tax exemption they didn’t use during life can be “ported” to the surviving spouse. In 2026, that exemption is $15 million per person, made permanent under the One Big Beautiful Bill Act. If your husband used none of his exemption, you can carry a combined shield of $30 million into your own estate. Skip the filing, and your personal exemption stays at $15 million. The other $15 million is gone forever.

The Statute That Makes It Real

Portability lives in Internal Revenue Code Section 2010(c)(5)(A), which requires the executor of the deceased spouse’s estate to make an affirmative election on a timely-filed Form 706, the United States Estate (and Generation-Skipping Transfer) Tax Return. The election was made permanent by the American Taxpayer Relief Act of 2012 and expanded by Revenue Procedure 2022-32, which extended the late-filing window to five years after the date of death for estates that weren’t otherwise required to file a 706.

Who Qualifies and Who Doesn’t

You qualify if you were legally married to a U.S. citizen or resident who died on or after January 1, 2011, and the estate files Form 706 electing portability. It doesn’t matter if the estate owed zero tax. In fact, the smaller estates are exactly the ones that skip the filing and lose the benefit.

You do not qualify if you were divorced at the time of death, if your spouse was a non-resident non-citizen, or if you have already remarried and your new spouse has since died. The rule allows only the DSUE from your last deceased spouse, so a second marriage can wipe out the first spouse’s ported exemption. Portability also does not apply to the generation-skipping transfer (GST) tax exemption, which is its own separate calculation.

How to Claim It, Step by Step

1. Confirm your spouse’s date of death and gather the estate inventory, including jointly held property, retirement accounts, and life insurance. The 706 requires you to value the entire gross estate, even assets that pass to you tax-free under the unlimited marital deduction.
2. Retain a CPA or estate attorney who has actually prepared Form 706. It runs roughly 30 pages plus schedules and is not a DIY project.
3. File Form 706 with the IRS. The standard deadline is nine months after the date of death, with an automatic six-month extension available via Form 4768.
4. On page 4, Part 6, check the box electing portability of the DSUE amount. Missing this box is the single most common way surviving spouses forfeit the exemption.
5. Keep the accepted return forever. Your estate’s executor will need it decades later to prove the DSUE amount when you die.

The Catch That Costs Families Millions

The trap is the deadline and the “we don’t need to file” assumption. If the surviving spouse’s estate is small today, families skip the 706 because no tax is due. Years later, a business sale, an inheritance, or decades of market growth push the survivor’s estate past $15 million, and the heirs discover the ported exemption was never elected. Revenue Procedure 2022-32 gives you a five-year window from the date of death to file a late portability-only return, but after that, you must request a private letter ruling from the IRS, which costs thousands and is not guaranteed.

One more quirk: portability locks in the dollar amount of unused exemption at the first death. It does not grow with inflation. If your husband died in 2021 with unused exemption, that fixed dollar figure is what you inherit, not a recalculated 2026 number. File the form anyway. It is the cheapest multi-million-dollar insurance policy your family will ever buy.

Contact [email protected] for any questions or corrections.