1. I. Except as provided in paragraph IV, in the case of any underpayment of estimated tax by a taxpayer, there shall be added to the tax for the taxable period an amount determined at the underpayment rate as determined from time to time pursuant to RSA 21-J:28, II, on the amount of the underpayment for the period of the underpayment.

2. II. For the purposes of paragraph I, the amount of the underpayment shall be the excess of:

   1. (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 for the taxable period; over

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

      II-a. For purposes of this section, "taxable period" means the calendar year or fiscal year which the taxpayer uses for federal income tax purposes, or that part of a year for which a return is made.

3. III. The period of the underpayment shall run from the date the installment was required to be paid to whichever of the following dates is the earlier:

   1. (a) The due date of the return; or
   2. (b) With respect to any portion of the underpayment, the date on which such portion is paid. For purposes of this paragraph, 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 subparagraph II(a).

4. IV. Notwithstanding the provisions of paragraphs I, II, and III, the penalty with respect to any installment shall not be imposed if the total amount of all payments of estimated tax made on or before the last date prescribed for the payment of the installment equals or exceeds the amount which would have been required to be paid on or before such date if the estimated tax were whichever of the following is the lesser:

   1. (a) The tax shown on the return of the taxpayer for the preceding taxable year, if a return showing a liability for tax was filed by the taxpayer for the preceding taxable year and such preceding year was a taxable year of 12 months.
   2. (b) An amount equal to the tax computed at the rates applicable to the taxable year but otherwise on the basis of the facts shown on the return of the taxpayer for, and the law applicable to, the preceding taxable year.

   3. (c)

      1. (1) An amount equal to 90 percent of the tax for the taxable year computed by placing on an annualized basis the taxable income:

         (A) For the first 3 months of the taxable year, in the case of the installment required to be paid in the fourth month,

         (B) For the first 3 months or for the first 5 months of the taxable year, in the case of the installment required to be paid in the sixth month.

         (C) For the first 6 months or for the first 8 months of the taxable year, in the case of the installment required to be paid in the ninth month, and

         (D) For the first 9 months or for the first 11 months of the taxable year, in the case of the installment required to be paid in the twelfth month of the taxable year.

      2. (2) For purposes of this paragraph, the taxable income shall be placed on an annualized basis by:

         (A) Multiplying by 12 the taxable income referred to in subparagraph IV(c)(1), and

         (B) Dividing the resulting amount by the number of months in the taxable year, whether 3, 5, 6, 8, 9, or 11, as the case may be, referred to in subparagraph IV(c)(1).

   4. (d) No amount, if this is the first tax period for which the taxpayer is required to file a tax return.
5. V. [Repealed.]
6. VI. Notwithstanding any other provisions of this section, if a taxpayer fails to pay taxes when they are due and is subsequently penalized under RSA 21-J:33 for his failure to pay, the failure to pay shall not be considered an underpayment of estimated tax, and no penalty shall be imposed upon the taxpayer under this section.

Source. 1985, 204:1; 414:10. 1988, 232:5. 1989, 50:2. 1991, 163:8, 9, 43, I. 1995, 268:2. 1999, 163:1, eff. Aug. 29, 1999. 2012, 14:1, eff. Dec. 31, 2012.