§ 5859. Assessment date, penalties, interest

(a) Any amount paid as estimated tax shall be deemed assessed upon the due date for the taxpayer's return for the taxable year (determined without regard to any extensions of time for filing such return).

(b) Except as provided in subsection (c) of this section, the taxpayer shall be liable for interest at the rate per annum established from time to time by the Commissioner pursuant to section 3108 of this title upon the amount of any underpayment of estimated tax.

(1) For purposes of this subsection, the amount of any underpayment of estimated tax shall be the excess of:

(A) the amount of the installment which would be required to be paid if the estimated tax were equal to 90 percent of the tax shown on the return for the taxable year, or, if no return were filed, 90 percent of the tax for such year, over

(B) the amount, if any, of the installment paid on or before the last date prescribed for payment.

(2) The period of the underpayment for which interest shall apply shall commence on the date the installment was required to be paid and shall terminate on the earlier of the following dates:

(A) the 15th day of the third month following the close of the taxable year; or

(B) with respect to any portion of the underpayment, the date on which such portion is paid. For purposes of this subdivision, a payment of estimated tax on any installment date shall be considered a payment of any previous underpayment only to the extent such payment exceeds the amount of the installment determined under subdivision (1)(A) of this subsection for such installment date.

(c) No interest for underpayment of any installment or estimated tax shall be imposed if the total amount of all such payments made on or before the last date prescribed for the payment of such installment equals or exceeds the amount which would have been required to be paid on or before such date if the estimated tax were the lesser of:

(1) an amount equal to the tax computed at the rate applicable to the taxable year but otherwise on the basis of the facts shown on the return for, and the law applicable to, the preceding taxable year; or

(2) an amount equal to 90 percent of the tax finally due for the taxable year.

(d) As used in subdivision (b)(1) and subsection (c) of this section, the term "tax" shall mean the excess of the tax imposed by this chapter over all amounts properly credited against such tax for the taxable year.

(e) The application of this subsection to taxable years of less than 12 months shall be in accordance with regulations prescribed by the Commissioner.

(f) The Commissioner may provide by regulation for a credit against estimated taxes for any taxable year of any amount determined by the taxpayer or by the Department to be an overpayment of the tax imposed by this title for a preceding taxable year. (Added 1975, No. 1 (Sp. Sess.), § 15, eff. Jan. 1, 1976; amended 1979, No. 105 (Adj. Sess.), § 5; 1981, No. 191 (Adj. Sess.), § 7; 2013, No. 73, § 22, eff. June 5, 2013.)