Okla. Stat. tit. 68, § 68-2385.17: Refund - Credit against estimated income tax -

Necessity for withholding certificate - Effect of refund.

Any amount withheld or paid by estimate in excess of the amount

due shown by a return filed by any employee shall be refunded to

said employee. The Tax Commission shall prescribe regulations

providing for the crediting against the estimated income tax for any

taxable year of the amount determined by the taxpayer or Tax

Commission to be an overpayment of the income tax for a preceding

taxable year. In order to obtain a credit against the tax due or a

refund, said employee shall attach to his return a legible copy of

the withholding certificate required to be furnished to said

employee by his employer, as provided for by Section 2385.3 of this

title. The Tax Commission may delay making any refund until such

time as the claim may be verified by audit, or if the employee is

delinquent in the filing of prior returns. The making of any refund

shall not be a conclusive finding of the tax due by any individual

but shall be made subject to the future audit of his return and the

determination of his liability.