When the attorney general has authority to institute an action pursuant to section 4, the attorney general may accept an assurance of discontinuance of any method, act, or practice from the person alleged to be engaged in or to have been engaged in a violation. The assurance may include the stipulation for the voluntary payment, by the person, of the costs of investigation, an amount for restitution to aggrieved persons, or both. An assurance of discontinuance shall be in writing and filed with the circuit court. The clerk of the court shall maintain a record of the filings. A matter closed pursuant to this section may be opened by the attorney general for further proceedings.