Mo. Rev. Stat. § 454.548: Processing fee permitted, amount.

In addition to any fees imposed pursuant to section 454.425 and if allowed by federal law, the division may charge and collect a fee of ten dollars from support received through the payment center for each order for every year or portion of a year during which payments are received by the payment center. Such fee shall be used to reimburse the state for the costs associated with processing support payments.