Mo. Rev. Stat. § 137.160

If the assessor discovers any real property, presumed to be subject to taxation, which has not been returned to him by the clerk, he shall assess such property and enter the same on the assessment list. And if, upon the return of such list to the clerk, it shall appear that any such real property has not been returned by the state tax commission, it shall be the duty of the clerk to advise the state tax commission of the facts, describing the property so returned by the assessor, and the state tax commission shall ascertain the true condition of such real property, and advise the said clerk thereof, who shall correct the records of his office in accordance with the facts in the case.