Mo. Rev. Stat. § 436.324

Within thirty days of the project reaching substantial completion, as defined in section 436.327, all retainage or substitute security shall be released by the owner to the contractor less an amount equal to one hundred fifty percent of the costs to complete any remaining items. Upon receipt of such retainage from the owner, the contractor shall within seven days release to each subcontractor that subcontractor's share of the retainage.