Okla. Stat. tit. 58, § 268

For property other than the probate estate passing directly upon the death of a decedent to another, by law, the executor or administrator of the estate of the decedent shall have the authority to bring an action in the district court having jurisdiction of the probate estate for the collection of any of the state or federal estate tax due and owing by the nonprobate beneficiaries after ten (10) days following service of notice by such executor or administrator upon such nonprobate beneficiary before suit is filed. Such notice shall state the amount of federal or state tax due to the executor or administrator by the nonprobate beneficiary. In such actions, the court costs and reasonable attorney fees may be assessed in favor of the prevailing party.