Okla. Stat. tit. 68 § 262
The Oklahoma Tax Commission may contract with private auditors or audit firms to audit the books of individuals, firms, or corporations which the Tax Commission believes may owe the State of Oklahoma additional tax monies. The Tax Commission may contract and may expend monies from the Oklahoma Tax Commission Reimbursement Fund to enter into such contracts. However, in no instance shall any such contract be paid upon a percentage basis, or on any basis whereby the compensation under the contract is dependent upon the amount of monies collected. Any such contract containing a provision whereby the compensation is conditioned upon or measured directly or indirectly by the amount of money collected shall be void and unenforceable. The Tax Commission may contract and may expend monies from the Oklahoma Tax Commission Reimbursement Fund in payment of a reasonable fee of the delivered funds in payment of contracts entered into with temporary service companies or professional collection agencies as necessary for the collection of delinquent taxes or other monies owed to the state. Such payment shall not be made until the funds have been deposited with the Tax Commission. Temporary employees or contractors hereunder shall not disclose confidential tax information except as authorized by Section 205 of this title, subject to the penalties contained therein.
Okla. Stat. tit. 68, § 262