Mo. Rev. Stat. § 273.160
The assessor for taxation purposes in each county and city of this state, annually at the time of assessing property as required by law, shall make diligent inquiry as to the number of dogs owned, harbored, or kept by any person so assessed. The assessor, on or before the thirty-first day of December of each year, shall make a complete report, on a blank form furnished by the county clerk or license collector, setting forth the name of every owner of any dog or dogs, how many of each sex are by him owned, or harbored, and if a kennel is maintained by any person such fact shall also be stated. The assessor, at the time of making the assessment, shall notify the owner of such dog that he must obtain a license for such dog as herein provided; but the neglect or failure so to notify such owner shall not relieve the owner from his duty to obtain such license.
§ 273.160, RSMo