# Portability: Definition and How It Works in California

> Portability lets a surviving spouse use the unused federal estate tax exemption of the spouse who died first.

Source: https://ridleylawoffices.com/estate-planning-glossary-california/portability/

By Eric Ridley, attorney, Ridley Law. Updated September 2026.

**Portability** lets a surviving spouse use the unused federal estate tax exemption of the spouse who died first. It isn’t automatic. The executor of the first spouse’s estate has to elect it on a timely federal estate tax return, even when no tax is owed on that estate.

## How it works in California

Portability is a creature of federal law, not California law, so it works the same way here as anywhere else. See [how portability plays out for California couples](https://ridleylawoffices.com/estate-tax-portability-california/) for the fuller picture. Under 26 U.S.C. § 2010(c)(2)(B) and (c)(4), a surviving spouse’s exclusion includes the deceased spouse’s unused exclusion amount.

Section 2010(c)(5)(A) allows that only if the executor elects it on a timely filed federal estate tax return. Miss that window under the general rule and the election is gone.

The IRS built in a backstop. Rev. Proc. 2022-32 lets an estate that was not otherwise required to file a federal estate tax return, and missed the deadline, make a simplified late portability election, as long as it files within five years of the date of death. After that window closes, reviving the election generally requires a private letter ruling, and that process is slower and less certain.

## Why it matters

Portability only helps if someone elects it, and a lot of estates never do because no return was otherwise required. For example, a surviving spouse whose late husband’s estate looked well under the filing threshold might assume there’s nothing to file. If no one elects portability on a timely, or five-year simplified-late, return, the survivor’s own estate later loses the benefit of the first spouse’s unused exemption, for good.

## Common mistakes

Assuming portability happens automatically because a spouse died. Skipping the estate tax return because the estate owes no tax, without realizing the return itself is what elects portability. Confusing portability with the generation-skipping transfer tax exemption, which doesn’t carry over between spouses the same way.

## Related terms

- [Marital Deduction](https://ridleylawoffices.com/estate-planning-glossary-california/marital-deduction/): the marital deduction and portability are both tools for deferring or reducing estate tax at the first spouse’s death.
- [Bypass Trust (AB Trust)](https://ridleylawoffices.com/estate-planning-glossary-california/bypass-trust/): older plans used a bypass trust to preserve the first spouse’s exemption before portability existed as an alternative.
- [Generation-Skipping Transfer Tax](https://ridleylawoffices.com/estate-planning-glossary-california/generation-skipping-transfer-tax/): the GST exemption is separate from portability and isn’t transferable between spouses.

Part of the [California estate planning glossary](https://ridleylawoffices.com/estate-planning-glossary-california/). For the full treatment, see [Estate Tax Portability in California: The 706 Most Families Skip](https://ridleylawoffices.com/estate-tax-portability-california/). For current federal and California figures, see [California Estate Planning Numbers 2026: Probate, Estate Tax, and Medi-Cal Limits](https://ridleylawoffices.com/2026-california-estate-law-changes/).