What Is Portability (DSUE) and How Do You Elect It?
Portability — formally the Deceased Spousal Unused Exclusion (DSUE) — is one of the most valuable but most often missed estate tax elections. It lets the surviving spouse add the first spouse’s unused federal estate tax exemption to their own. In 2026, that can mean a combined $30 million federal shelter.
How portability works
When the first spouse dies, the executor files IRS Form 706. Even if no estate tax is owed, the form is used to calculate and elect the unused exclusion amount. The surviving spouse can then apply that DSUE amount to lifetime gifts or to their own estate.
Deadline and procedure
Form 706 is generally due 9 months after death, with an automatic 6-month extension available. The portability election must be made on a timely filed Form 706. Missing the deadline usually forfeits the DSUE permanently.
Limitations of portability
Portability applies only to the estate and gift tax exemption, not to the generation-skipping transfer (GST) exemption. Some states do not recognize portability, so married couples in those states may need a credit-shelter trust instead.
Portability in action
If the first spouse dies with a $5 million estate and a $15 million exemption, $10 million of exemption is unused. The surviving spouse can add that $10 million to their own $15 million, sheltering up to $25 million from federal estate tax.
Try your own numbers in the Estate Tax Simulator or Federal Estate Tax Calculator.