Mo. Rev. Stat. § 249.947: Cause of action to set aside assessment, time limitation.

No cause of action to set aside the assessments made under sections 249.925 to 249.955 or to otherwise question the validity of the proceedings relating thereto shall be brought after the expiration of ninety days from the date of mailing of notice to property owners of the assessments required by sections 249.941 to 249.945.