Mo. Rev. Stat. § 70.670: Early retirement, application — requirements — option — benefits, how computed.

1. Any member in service who has not attained his minimum service retirement age may retire with an early allowance provided for in subsection 2 of this section, upon his written application to the board setting forth at what time, not less than thirty days nor more than ninety days subsequent to the execution and filing thereof, he desires to be retired; provided, that at the time of his separation from service and the time so specified for his retirement, the member's age shall be within five years of his minimum service retirement age and he shall have five or more years of credited service in force, and notwithstanding that during such period of notification he may have separated from service. He shall have the right to elect an option provided for in section 70.660.

2. Upon early retirement a member shall receive a certain percent of an allowance provided for in section 70.655. Such percent shall be one hundred percent reduced by: One-half of one percent multiplied by the number of months by which his age at early retirement is younger than his minimum service retirement age.