§ 143.731 RSMo — Interest on underpayments

1. If any amount of tax imposed by sections 143.011 to 143.996 , including tax withheld by an employer, is not paid on or before the last date prescribed for payment, interest on such amount at the rate determined by section 32.065 shall be paid for the period from such last date to date paid. No interest shall be imposed if the amount due is less than one dollar nor shall this section apply to any failure to pay estimated income tax under section 143.541 .

2. For purposes of this section, the last date prescribed for the payment of tax shall be determined without regard to any extension of time.

3. If the taxpayer has filed a waiver of restrictions on the assessment of a deficiency and if notice and demand by the director of revenue for payment of such deficiency is not made within thirty days after the filing of such waiver, interest shall not be imposed on such deficiency for the period beginning immediately after such thirtieth day and ending with the date of notice and demand.

4. Interest prescribed under this section on any tax, including tax withheld by an employer, shall be paid on notice and demand and shall be assessed, collected, and paid in the same manner as taxes. Any reference in sections 143.011 to 143.996 to the tax imposed by sections 143.011 to 143.996 shall be deemed also to refer to interest imposed by this section on such tax.

5. Interest shall be imposed under this section in respect to any penalty or addition to tax only if such penalty or addition to tax is not paid within ten days of the notice and demand therefor, and in such case interest shall be imposed only for the period from the date of the notice and demand to the date of payment.

6. If notice and demand is made for the payment of any amount due under sections 143.011 to 143.996 and if such amount is paid within ten days after the date of such notice and demand, interest under this section on the amount so paid shall not be imposed for the period after the date of such notice and demand.

7. If any portion of a tax is satisfied by credit of an overpayment, then no interest shall be imposed under this section on the portion of the tax so satisfied for any period during which, if the credit had not been made, interest would have been allowable with respect to such overpayment.

8. If any portion of a tax finally determined to be due is satisfied by a deposit under subsection 2 of section 143.631 , then no interest shall be imposed under this section on the portion of the tax so satisfied for the period from the date the director of revenue received and accepted the deposit.

9. Any portion of the tax imposed by sections 143.011 to 143.996 or any interest, penalty, or addition to tax which has been erroneously refunded and which is recoverable by the director of revenue shall bear interest at the rate determined by section 32.065 from the date of payment of the refund.

10. Interest prescribed under this section may be assessed and collected at any time during the period within which the tax, penalty, or addition to tax to which such interest relates may be assessed and collected respectively.