1. In case of failure to file any return required under sections 144.600 to 144.745 on or before the date prescribed therefor (determined with regard to any extension of time for making a return), unless it is shown that such failure is due to reasonable cause and not the result of willful neglect, evasion, or fraudulent intent, there shall be added to the amount required to be shown as tax on such return five percent of the amount of such tax if the failure is not for more than one month, with an additional five percent for each additional month, or fraction thereof, during which such failure continues, not exceeding twenty-five percent in the aggregate; except that, when the gross sales tax exceeds two hundred fifty dollars in any one month for which a taxpayer must file a monthly return, there shall be no late penalty assessed for the first month in which the return is due. For purposes of this section, the amount of tax required to be shown on the return shall be reduced by the amount of any part of the tax which is paid on or before the date prescribed for payment of the tax.

2. In case of failure to pay any tax required under sections 144.600 to 144.745 on or before the date prescribed therefor (determined with regard to any extension of time for payment), unless it is shown that such failure is due to reasonable cause and not the result of willful neglect, evasion, or fraudulent intent, there shall be added to the tax an amount equal to five percent of the deficiency.

3. The provisions in subsections 1 and 2 of this section shall be in addition to any interest provided for in this chapter.