Mo. Rev. Stat. § 376.391: Co-payments for chiropractic services, cap.

A health benefit plan or health carrier, as defined in section 376.1350, including but not limited to preferred provider organizations, independent physicians associations, third-party administrators, or any entity that contracts with licensed health care providers shall not impose any co-payment that exceeds fifty percent of the total cost of providing any single chiropractic service to its enrollees.