Mo. Rev. Stat. § 454.1539
A tribunal of this state shall credit amounts collected for a particular period pursuant to any child support order against the amounts owed for the same period under any other child support order for support of the same child issued by a tribunal of this state, another state, or a foreign country.
(L. 2011 H.B. 260)
Effective 6-15-16, see § 454.1728