Mo. Rev. Stat. § 115.135

115.135. Persons entitled to register, when — identification required — military service, registration, when. — 1. Any person who is qualified to vote, or who shall become qualified to vote on or before the day of election, shall be entitled to register in the jurisdiction within which he or she resides. In order to vote in any election for which registration is required, a person must be registered to vote in the state of Missouri no later than 5:00 p.m., or the normal closing time of any public building where the registration is being held if such time is later than 5:00 p.m., on the fourth Wednesday prior to the election, unless the voter is an interstate former resident, a new resident, or a covered voter, as defined in section 115.275 . Any person registering after such date shall be eligible to vote in subsequent elections.

2. A person applying to register with an election authority or a deputy registration official shall identify himself or herself by presenting a copy of a birth certificate, a Native American tribal document, other proof of United States citizenship, a valid Missouri drivers license or other form of personal identification at the time of registration.

3. Except as provided in federal law or federal elections and in section 115.277 , no person shall be entitled to vote if the person has not registered to vote in the jurisdiction of his or her residence.

4. A covered voter as defined in section 115.275 who has been discharged from military service, has returned from a military deployment or activation, or has separated from employment outside the territorial limits of the United States after the deadline to register to vote, and who is otherwise qualified to register to vote, may register to vote in an election in person before the election authority until 5:00 p.m. on the Friday before such election. Such persons shall produce sufficient documentation showing evidence of qualifying for late registration pursuant to this section.

(L. 1977 H.B. 101 § 7.015, A.L. 1982 S.B. 526, A.L. 1985 H.B. 620, A.L. 1988 H.B. 933, et al., A.L. 1993 H.B. 551 & 552, A.L. 1994 H.B. 1411, A.L. 2002 S.B. 675, A.L. 2003 H.B. 511, A.L. 2005 H.B. 353, A.L. 2015 S.B. 34 & 105, A.L. 2022 H.B. 1878)