Mo. Rev. Stat. § 384.054: Delinquent tax, penalty, interest.

Any tax imposed by sections 384.011 to 384.071 which is delinquent in payment shall be subject to a penalty of one percent of the tax per diem up to ten percent of the tax. Any delinquent tax shall bear interest at the rate determined under section 32.065 from the time such tax is due.