Mo. Rev. Stat. § 115.297
Before the precinct registers are delivered to the polling places for an election, the election authority shall record in the precinct registers those voters who have submitted an absentee ballot and are ineligible to vote at the polls. On election day, the election authority shall notify the appropriate election judges of any absentee ballot received by the election authority not previously recorded in a precinct register. The election authority shall record the fact in the appropriate precinct register and shall not allow any person who has voted an absentee ballot in the election to vote at the polls on election day. After the election and before convening the verification board, the election authority shall record in the precinct registers those voters whose absentee ballots were received too late to permit previous recording in the precinct registers. If it is determined that any voter submitted an absentee ballot and voted at the polls on election day, the election authority shall certify the fact and the name of the voter to the verification board. Such certificate shall be included with the abstracts drawn by the verification board.
§ 115.297, RSMo