Mo. Rev. Stat. § 660.330
Any entity shall, upon request by the department, inform the department of the last known address of any person or of any moneys deposited on behalf of any person named in the request who owes a duty of support to or for any applicant for or recipient of public assistance wherein such support obligation has been assigned to the department or any of its divisions either by written assignment or operation of law and the department or division has obtained an unsatisfied judgment for such child support and after ten days' written notice has been provided to such person. Before any such information is provided, the department shall provide to the entity an affidavit with specificity that all of the requirements of this section have been met.
§ 660.330, RSMo