Okla. Stat. tit. 68 § 615
Any person licensed under the Motor Fuel/Diesel Fuel Importer for Use Law shall be entitled to a credit equivalent to the tax rate per gallon on all gasoline or diesel fuel upon which the Oklahoma gasoline or diesel fuel tax has been paid and which has thereafter been consumed in motor vehicles outside this state. When the amount of credit provided in this section to which the person is entitled for any calendar quarter exceeds the amount of tax for which such person is liable for gasoline or diesel fuel consumed in Oklahoma in such vehicles during the same quarter, such excess shall, under rules promulgated by the Corporation Commission, be allowed as a credit if used within twenty-four (24) months from the first day of any calendar quarter against the tax for which such person would be otherwise liable for any of the succeeding quarters; or, upon claim filed with the Commission within twenty-four (24) months from the first day of any calendar quarter in which the gasoline or diesel fuel was used, such excess, less one and seven-tenths percent (1.7%) of gasoline tax levied and two percent (2%) of diesel fuel tax levied pursuant to Section 500.4 of this title, may be refunded. Application for refund must be supported by evidence of the mileage traveled and the gallonage consumed and satisfactory evidence of the tax-paid purchases. Refund vouchers shall be paid from current collections derived from the tax levied under which the tax refund claims have been allowed, and a portion of such current collections as are necessary to pay such refund is hereby appropriated.
Okla. Stat. tit. 68, § 615