Missouri Code of State Regulations
Title 20 - DEPARTMENT OF COMMERCE AND INSURANCE
Division 500 - Property and Casualty
Chapter 6 - Workers' Compensation and Employers' Liability
Section 20 CSR 500-6.600 - Effective Date of Experience Rating Modification

(1) An insurer shall not implement an increase in premiums through the application of an experience rating modification factor, assigned risk adjustment program (ARAP) factor, or other surcharge authorized by the Department of Insurance after the effective date of the policy (or at the anniversary date of the policy, if different), unless the insured is issued an endorsement describing the potential of the pending increase when the policy is issued.

(2) An insurer shall not apply an increase specified in section (1) of this rule retroactively.

(3) Any factor or other surcharge specified in section (1) applied after the policy effective date (or anniversary rating date, if different) which increases premiums shall not become effective until sixty (60) days after the date the insurer provides written notification to the insured of the increase.

(4) Any modification of a type specified in section (1) of this rule but which results in a premium reduction shall not be subject to the restrictions in sections (2) and (3) and shall be retroactive to the policy inception date.

(5) For the purposes of the rates filed in compliance with section 287.320, RSMo, it shall be considered unreasonable and inadequate to develop rates based on data which excludes premiums that would have been collected except for the restrictions set forth in this rule. Actuarial estimates would be acceptable to demonstrate the impact of this rule.

(6) Sections (2) and (3) shall not apply when any delay in the application of the modification factor increase or surcharge increase is due to the policyholder's failure in providing necessary data for the development of the factor or surcharge, provided that requests for data are timely and adequately documented.

(7) This rule is applicable only to portions of an insurance policy which provide coverage for risks principally localized in Missouri.