When interest is required under this section, interest is computed at the rate specified in section 270C.40.
If a tax under this chapter is not paid within the time named by law for payment, the unpaid tax bears interest from the date the tax should have been paid until the date the tax is paid.
When an extension of time for payment has been granted, interest must be paid from the date the payment should have been made, if no extension had been granted, until the date the tax is paid.
When a taxpayer is liable for additional taxes because of a redetermination by the commissioner, or for any other reason, the additional taxes bear interest from the time the tax should have been paid, without regard to an extension allowed, until the date the tax is paid.
In the case of an erroneous refund or credit, interest begins to accrue from the date the refund or credit was paid unless the erroneous refund or credit results from a mistake of the department, in which case no interest or penalty is imposed, unless the deficiency assessment is not satisfied within 60 days of the order.
Notwithstanding section 549.09, if judgment is entered in favor of the commissioner with regard to any tax under this chapter, the judgment bears interest at the rate given in section 270C.40 from the date the judgment is entered until the date of payment.
(b) A penalty not included in paragraph (a) bears interest only if it is not paid within ten days from the date of the notice. In that case interest is imposed from the date of notice to the date of payment.
Interest must be paid on an overpayment refunded or credited to the taxpayer from the date of payment of the tax until the date the refund is paid or credited.