The Oklahoma Supreme Court has held that a decedent’s unused federal estate tax exclusion amount (referred to in IRC section 2010 as the “deceased spousal unused exclusion amount,” or “DSUE”) is an asset of the decedent’s estate that the administrator of the estate has a fiduciary duty to preserve for the benefit of the surviving spouse by filing a federal estate tax return, even though a prenuptial agreement barred the surviving spouse from being a beneficiary of the estate.  (The surviving spouse had agreed to pay the costs of the required estate tax return.)  In the Matter of the Estate of Vose, 2017 OK 3, 390 P.3d 238 (Okla. 1/31/2017).