Mo. Rev. Stat. § 137.335: Blanks for assessment to be designed by state tax commission — time of making assessment.

The state tax commission shall design the necessary assessment blanks, which shall contain a classification of all tangible personal property, and the blanks shall be furnished to the county assessor sixty days before January first of each year. After receiving the form of the assessment blanks, the assessor or his deputies shall, between the first day of January and the first day of July of each year, make and complete a list of all real and tangible personal property taxable by the county and assess the property at its true value in money.