Mo. Rev. Stat. § 86.344

On or before the first day of March of each year the board of trustees shall certify to the board of estimate and apportionment of the city the amounts which will become due and payable during the year next following for expenses pursuant to subsection 2 of section 86.343 and the cost of benefits as determined pursuant to section 86.337. The amounts so certified shall be appropriated by the city and transferred to the retirement system in equal payments in the first six months of the ensuing year.