Mo. Rev. Stat. § 88.913
In any suit or proceedings to enforce the collection of any special tax bill issued under the provisions of sections 88.863 to 88.910 it shall only be necessary for the owner thereof to charge in the petition that such amount is due by the defendant to the plaintiff for a certain improvement made by virtue of certain ordinances, giving their title and date of adoption; provided, that nothing in said sections shall be so construed as to prevent any defendant from pleading and proving in reduction of any bill any mistake or error in the amount thereof, or that the work therein mentioned was not done in a good and workmanlike manner; and provided further, that if any party shall plead any mistake or error in the amount of the bill, or that the work was not done in a workmanlike manner, and that such party, before the commencement of the suit, tendered to the contractor, or holder of the bill, the full value of the work done, and shall establish the same on the trial, the recovery shall only be in the amount so tendered, and judgment for costs shall be rendered against the plaintiff; provided further, that if it be pleaded and proved that the work for which the bill was issued was not done according to the terms of the contract made by the contractor with the city, then the plaintiff or plaintiffs shall recover thereon only the actual value of the work done, with interest at six percent from date, if of any value; and if not of any value, the judgment shall be for the defendant. No suit for the collection of any tax bill shall be defeated or affected by any irregularity affecting any other bill, or matter rendering any other bill invalid in whole or in part; provided further, that if at any time it is found that there has been any error in the issuance of any tax bills or in any assessment, or in the mode or manner of any assessment, the same shall be corrected and a reassessment made (if necessary to correct the mistake) by the proper officials, and said reassessment shall be as binding and in all respects the same as if no previous assessments had been made or tax bills issued.
§ 88.913, RSMo