Mo. Rev. Stat. § 454.472

No garnishment, withholding, or other financial legal proceeding under chapter 454 to enforce a support order as defined in section 454.460 shall be levied or maintained by the family support division against a party who alleges that no current or unpaid child support is due if, after review of the allegations and evidence, the division determines that no current or unpaid child support is due. The enforcement action may continue pending a review by the division, and the division may only levy an enforcement action if current or unpaid support should later become due and owing. The division shall advise a party to a support obligation being enforced by the division of the amount currently due under the support order and how that amount was calculated upon request.