Portability
A rule that allows a surviving spouse to use their deceased spouse's unused estate tax exemption in addition to their own. This effectively doubles the amount that can pass tax-free.
Legal Definition
Under IRC ยง2010(c)(4), the ability of a surviving spouse to elect to use the deceased spousal unused exclusion (DSUE) amount, effectively increasing the surviving spouse's applicable exclusion amount by the unused portion of the predeceased spouse's exemption.
Practical Example
When the first spouse dies in 2024, they only use $5 million of their $13.61 million exemption. The surviving spouse can 'port' the unused $8.61 million, giving them a total exemption of $22.22 million ($13.61M + $8.61M).