Amends the Illinois Insurance Code. Provides that every insurer that amends, delivers, issues, or renews a group or individual policy of accident and health insurance or a qualified health plan offered through the health insurance marketplace in the State and Medicaid managed care organizations providing coverage for hospital or medical treatment shall provide coverage for medically necessary treatment of mental, emotional, nervous, or substance use disorders or conditions. Provides that an insurer shall not limit benefits or coverage for medically necessary services on the basis that those services should be or could be covered by a public program. Provides that an insurer shall base any medical necessity determination or the utilization review criteria on current generally accepted standards of mental, emotional, nervous, or substance use disorder or condition care. Provides that in conducting utilization review of covered health care services and benefits for the diagnosis, prevention, and treatment of mental, emotional, and nervous disorders or conditions in children, adolescents, and adults, an insurer shall exclusively apply the criteria and guidelines set forth in the most recent versions of the treatment criteria developed by the nonprofit professional association for the relevant clinical specialty. Provides that an insurer shall not apply different, additional, conflicting, or more restrictive utilization review criteria than the criteria and guidelines set forth in the treatment criteria. Provides that the Director may, after appropriate notice and opportunity for hearing, assess a civil penalty between $5,000 and $20,000 for each violation. Amends the Health Carrier External Review Act. Provides that the independent review organization shall comply with specified requirements for an adverse determination or final adverse determination involving mental, emotional, nervous, or substance use disorders or conditions. Makes other changes. Effective immediately.