5. a. In case of any underpayment of an installment payment by a taxpayer, there shall be added to the tax for the fiscal or calendar accounting year an amount determined by applying the rate established in this section to the amount of the underpayment for the period of the underpayment.

b. For purposes of subsection a., the amount of underpayment shall be the excess of:

(1) The lesser of the amount of the installment payment which would be required to be paid if all installment payments and all payments of tax made pursuant to subsection a. of section 12 of P.L.2002, c.40 (C. 54:10A-15.11) and credited to the taxpayer pursuant to subsection b. of section 12 of P.L.2002, c.40 were equal to 90% of the tax shown on the return for the fiscal or calendar accounting year, or if no return was filed, 90% of the tax for that year, or 100% of the tax shown on the tax return of the taxpayer for the preceding taxable year over

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

c. For purposes of subsection a., the period of the underpayment shall run from the date the installment payment was required to be paid to whichever of the following dates is the earlier:

(1) The fifteenth day of the fifth month after the close of the fiscal or calendar accounting year.

(2) With respect to any portion of the underpayment, the date on which that portion is paid.

For purposes of this subsection, a payment of any installment payment shall be considered a payment of any previous underpayment only to the extent that payment exceeds the amount of the installment payment determined under subsection b. (1) for that installment payment.

d. Notwithstanding the provisions of the preceding subsections, the addition to the tax with respect to any underpayment of any installment payment shall not be imposed if the total amount of all installment payments made on or before the last date prescribed for the payment of that installment equals or exceeds the amount which would have been required to be paid on or before that date if the total amount of all installment payments were the lesser of (1) or (2) as follows:

(1) An amount equal to the tax computed at the rates applicable to the current fiscal or calendar accounting year but otherwise on the basis of the facts shown on the return of the taxpayer for, and the law applicable to, the preceding fiscal or calendar accounting year; or

(2) An amount equal to 90% of the tax for the current fiscal or calendar accounting year computed by placing on an annualized basis the taxable entire net income and entire net worth:

(a) For the first three months of the current fiscal or calendar accounting year, in the case of the installment payment required to be paid in the fourth month,

(b) For the first three months or for the first five months of the current fiscal or calendar accounting year, in the case of the installment payment required to be paid in the sixth month,

(c) For the first six months or for the first eight months of the current fiscal or calendar accounting year, in the case of the installment payment required to be paid in the ninth month,

(d) For the first nine months or for the first 11 months of the current fiscal or calendar accounting year, in the case of the installment payment required to be paid in the 12th month, and

(e) For the last three months of the preceding taxable year, in the case of the installment payment required to be paid in the first month of the current fiscal or calendar accounting year.

e. Any taxpayer who shall fail to pay, or shall underpay by more than 10% of the amount due, any installment payment required pursuant to this act, shall pay, in addition to the tax, interest on the amount of underpayment as provided in the State Tax Uniform Procedure Law, R.S.54:48-1 et seq.; provided, however, a taxpayer may petition the Director of the Division of Taxation to waive this interest if the taxpayer demonstrates undue hardship, good cause, or any other reason as may be provided for waiving penalties and interest under the State Tax Uniform Procedure Law, R.S.54:48-1 et seq.

L.1981,c.184,s.5; amended 1981, c.343, s.1; 1987, c.76, s.50; 1998, c.106, s.1; 2005, c.288, s.2; 2023, c.96, s.10.