Mo. Rev. Stat. § 115.179: Registration records to be canvassed, when.

1. The election authority shall have the registration records of all precincts in its jurisdiction canvassed every two years in accordance with subsection 3 of section 115.163 and that it be completed no later than ninety days prior to the date of a primary or general election for federal office. The election authority may utilize postal service contractors under the federal National Change of Address program to canvass the records.

2. In each jurisdiction without a board of election commissioners, the county clerk shall have the registration records of all precincts in its jurisdiction canvassed every two years in accordance with subsection 3 of section 115.163 and that it be completed no later than ninety days prior to the date of a primary or general election for federal office.