Mo. Rev. Stat. § 139.350

Every collector-treasurer in a county having a township organization, upon receiving the tax book and warrant from the county clerk, shall proceed in the following manner to collect the same; and the collector-treasurer shall mail to all resident taxpayers, at least fifteen days prior to delinquent date, a statement of all real and tangible personal property taxes due and assessed on the current tax books in the name of the taxpayers. Collector-treasurers shall also mail tax receipts for all the taxes received by mail.