Okla. Stat. tit. 58, § 635

Before any decree of distribution of an estate is made, the district court must be satisfied, by the oath of the executor or administrator, or otherwise, that all state, county, school and municipal taxes, legally levied upon personal property of the estate, and all income and estate taxes due the State of Oklahoma have been fully paid or arrangements satisfactory to the court have been made to secure the payment of same. For deaths occurring on or after January 1, 2010, no release of estate tax liability is necessary pursuant to Section 5 of this act.