Portability Is Not Automatic, And One Mistake Can Zero It Out

Portability is widely described as the simplest way for married couples to preserve a combined estate and gift tax exclusion.

That simplicity is partly true.

But the election is not automatic. It is a filing position. And it can fail if the return is not prepared correctly, even when no estate tax is due.

What portability actually does

When one spouse dies, the estate can transfer the unused portion of that spouse’s exclusion to the surviving spouse.
That transferred amount is the deceased spousal unused exclusion (DSUE).

Two details matter:

  • DSUE is determined as of the year of the first spouse’s death and is not increased for inflation later.

  • The surviving spouse’s own exclusion can adjust annually, but DSUE stays fixed.

The portability election deadline

The statutory deadline to file Form 706 and elect portability is nine months after the date of death, with an automatic six month extension available via Form 4768 if filed on time.

There is also a major relief rule for estates below the filing threshold:

  • If an estate is under the applicable filing threshold, the executor may file a late portability election by the fifth anniversary of the date of death if the return is properly labeled as required by the applicable revenue procedure.

  • The filing threshold is year specific. The source notes $15 million for 2026 and $13.99 million for 2025.

If the estate does not qualify for this relief, extension relief may require a private letter ruling process that can be costly.

The trap: “simplified reporting” is not a free pass

When Form 706 is filed solely to elect portability, simplified reporting rules can reduce valuation burden.

But simplified reporting is not universal.
It is available only in narrow situations where the entire estate is left to:

  • the surviving spouse, and/or

  • qualified charity, and/or

  • certain marital or charitable trust structures described in the rules.

If value is needed to determine what passes to non marital or non charitable beneficiaries, simplified reporting may not apply.

When simplified reporting is not allowed, global estimates can be fatal. The return must include actual fair market values for the assets.

Why this matters: the portability election can be disallowed later

The most dangerous feature of a portability error is timing.

The election failure often shows up only when the surviving spouse dies, when DSUE is needed to reduce estate tax.
At that point, it is too late to fix the original return posture.

The source describes an example where simplified reporting was used even though the estate plan included specific bequests and trusts that required valuation to determine the split among beneficiaries.
The portability election was disallowed, the DSUE was lost, and the surviving spouse’s estate faced significant additional estate tax.

The real executor instruction most families miss

If your plan relies on portability, your executor needs clear written authority to:

  • file Form 706 for portability even if no estate tax is due

  • obtain appraisals and professional valuations when needed

  • hire professional tax support to complete a complete and properly prepared return

This is not a paperwork preference. It is a control. The goal is to avoid a DSUE loss caused by incomplete preparation.

Decision screen: do you need full valuations or can you simplify

Before you assume simplified reporting applies, ask:

  • Does the estate plan include specific bequests to children, grandchildren, or friends?

  • Does the plan fund non marital or non charitable trusts?

  • Do you need asset values to determine what passes to different beneficiaries?

If yes, treat simplified reporting as high risk. Plan for real valuations.

What to do next

If portability matters for your family, the highest leverage move is to review:

  • whether the estate is likely to be below the filing threshold

  • whether the plan structure allows simplified reporting

  • whether executor instructions authorize valuations and professional preparation

  • whether any prior portability return was filed timely and properly

Contact us today.

If you are a Brothers Tax client, your return includes ProtectionPlus support, subject to program terms, including audit assistance and identity theft restoration.

Disclosure: Educational only; not tax or legal advice. Outcomes depend on facts, documents, and filing posture.