Okla. Stat. tit. 68 § 722
Any person licensed as a special fuel dealer or special fuel user shall be entitled to a credit equivalent to the tax rate per gallon on all special fuels upon which the Oklahoma special fuel tax has been paid and which has thereafter been consumed in motor vehicles outside the State of Oklahoma. When the amount of credit herein provided to which the dealer or user is entitled for any calendar month exceeds the amount of tax for which such dealer or user is liable for special fuels consumed in Oklahoma in such vehicles during the same month, such excess shall, under regulations promulgated by the Oklahoma Tax Commission, be allowed as a credit against the tax for which such dealer or user would be otherwise liable for any of the succeeding months; or, upon claim filed with the Oklahoma Tax Commission within one (1) year from the first day of any calendar month in which said special fuel was used, such excess 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, § 722