Okla. Stat. tit. 68, § 2364

A. The Oklahoma taxable income or loss of an estate, trust or any beneficiary of either shall be the same portion of that reported for federal income tax purposes as the Oklahoma income, gains, losses or deductions determined under applicable provisions of this act for said estate, trust and/or beneficiary bears to the federal income, gains, losses or deductions. Amounts allowable under the Oklahoma Estate Tax Law as deductions in computing the taxable estate of a decedent shall not be allowed as deductions in computing the taxable income of the estate or of any other person unless there is filed, as provided in Internal Revenue Code, Section 642, or any provisions comparable thereto, the statement required therein and if such waiver is filed then to the extent allowed as a deduction for income tax purposes, such amount shall not be allowed for estate tax purposes. B. A beneficiary of a trust shall exclude from Oklahoma taxable income any excess distributions by trusts required to be included in the beneficiary's federal taxable income by reason of Sections 665 through 669 of the Internal Revenue Code, or any provisions comparable thereto.