The IRC section 2010(c)(2) allows for a spouse's unused portion of their exclusion amount to be added to the surviving spouse's exclusion amount. 


Exclusion amounts are portable. This means that if a deceased spouse does not use all of their exclusion amount, the surviving spouse may use the remainder in addition to their own exclusion amount. One requirement, however, is that the estate of the deceased spouse must timely file an estate tax return that specifies that the remaining portion is portable.

This is an important provision because many people use the marital deduction to transfer their property to the surviving spouse, as a way to not pay gift and estate taxes, and do not use any part of their exclusion amount. This will mean that the surviving spouse’s exclusion amount can double.