Mo. Rev. Stat. § 50.1100
Any member may retire at any time after the end of the month during which the member becomes eligible to retire pursuant to the provisions of section 50.1050, and upon the member's submission of a 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 of the application, the member desires to be retired. The payment of the annuity shall begin as of the first day of the calendar month coincident with or next following the date specified by the member, but shall begin no later than the required beginning date. Notwithstanding the member's eligibility, no member shall receive such annuity while serving as an employee of the county; except that, a member may work as an employee of the county for less than one thousand hours in a calendar year and be eligible to receive the annuity. Such part-time service shall not increase or change the member's annuity.
§ 50.1100, RSMo
Effective 1/1/2000