Mo. Rev. Stat. § 86.354: Benefit vested and nonforfeitable, when — forfeitures, use of.

A member's benefit shall be one hundred percent vested and nonforfeitable upon the first of the following to occur:

(1) The member's attainment of age fifty-five, the normal retirement age; or

(2) The member's completion of twenty years of creditable service regardless of age; or

(3) The termination of the plan established pursuant to sections 86.200 to 86.366, to the extent the plan is funded.

Forfeitures of any nature under such plan shall not be used to increase the benefits of any member, but shall be used to reduce the city's contributions pursuant to section 86.243.