Mo. Rev. Stat. § 53.040: Bond.

Every assessor (except the assessor of St. Louis City) before entering upon the duties of his office, shall give a surety company bond in a sum of not less than one thousand dollars, to be paid by the county or township, the amount to be fixed by the commission or clerk, as the case may require, conditioned for the faithful performance of the duties of his office, which bond shall be deposited in the office of the clerk of the county commission.