(a) Except as otherwise provided in this section, in the case of any underpayment of estimated tax by an individual, there shall be added to the tax an amount determined by applying interest (1) at the rate of one per cent per month or fraction thereof, (2) to the amount of the underpayment, (3) for the period of the underpayment.

(b) For purposes of subsection (a) of this section, the amount of the underpayment shall be the excess of the required installment, over the amount, if any, of the installment paid on or before the due date for the installment. For purposes of subsection (a) of this section, the period of the underpayment shall run from the due date for the installment to whichever of the following dates is earlier: The fifteenth day of the fourth month of the next succeeding taxable year, or, with respect to any portion of the underpayment, the date on which such portion is paid. For purposes of this subsection, a payment of estimated tax shall be credited against unpaid required installments in the order in which such installments are required to be paid.

(c) For purposes of this section, there shall be four required installments for each taxable year. The due date for the first required installment is the fifteenth day of the fourth month of the taxable year. The due date for the second required installment is the fifteenth day of the sixth month of the taxable year. The due date for the third required installment is the fifteenth day of the ninth month of the taxable year. The due date for the fourth required installment is the fifteenth day of the first month of the next succeeding taxable year.

(d) (1) Except as provided in subdivision (2) of this subsection, the amount of any required installment shall be twenty-five per cent of the required annual payment, as defined in section 12-701.

(2) (A) In the case of any required installment, if the taxpayer establishes that the annualized income installment is less than the amount determined under subdivision (1) of this subsection, the amount of such required installment shall be the annualized income installment, and any reduction in a required installment resulting from the application of this subdivision shall be recaptured by increasing the amount of the next required installment by the amount of such reduction and by increasing subsequent required installments to the extent that the reduction has not previously been recaptured under this subdivision. (B) In the case of any required installment, the annualized income installment is the excess, if any, of (i) an amount equal to the applicable percentage of the tax for the taxable year computed by placing on an annualized basis the Connecticut taxable income and the adjusted federal alternative minimum taxable income for months in the taxable year ending before the due date for the installment, over (ii) the aggregate amount of any prior required installments for the taxable year. (C) For purposes of this subdivision, the applicable percentage for the first required installment is twenty-two and one-half, the applicable percentage for the second required installment is forty-five, the applicable percentage for the third required installment is sixty-seven and one-half, and the applicable percentage for the fourth required installment is ninety.

(e) The application of this section to taxable years of less than twelve months shall be in accordance with regulations adopted by the commissioner.

(f) In applying this section to a taxable year beginning on any date other than January first, there shall be substituted, for the months specified in this section, the months which correspond thereto.

(g) At the election of the individual, any installment of the estimated tax may be paid prior to the date prescribed for its payment.

(h) Payment of the estimated income tax, or any installment thereof, shall be considered payment on account of the income tax imposed under this chapter for the taxable year.

(i) If an individual has paid as an installment of estimated tax an amount in excess of the amount determined to be the correct amount of such installment, such amount shall be credited against any unpaid installment or against the tax. If the amount already paid, whether or not on the basis of installments, exceeds the amount determined to be the correct amount of the tax, then, unless the individual has given written notice to the commissioner that such overpayment is to be refunded, such overpayment shall be credited against any installment of estimated tax due for the next succeeding taxable year.

(j) (1) No addition to tax shall be imposed under subsection (a) of this section for any taxable year if the tax shown on the return for such taxable year, or, if no return is filed, the tax, reduced by the tax withheld under this chapter, is less than one thousand dollars.

(2) No addition to tax shall be imposed under said subsection (a) for any taxable year if (A) the preceding taxable year was a taxable year of twelve months and (B) the individual did not have any liability for tax for the preceding taxable year and throughout such year the individual was (i) a resident individual or (ii) a nonresident individual or part-year resident individual with income, gain, loss or deduction derived from or connected with sources within this state.

(k) For purposes of applying this section, the tax withheld under this chapter shall be deemed a payment of estimated tax, and an equal part of such tax withheld shall be deemed paid on each due date for such taxable year, unless the taxpayer establishes the dates on which such tax was actually withheld, in which case the tax so withheld shall be deemed payments of estimated tax on the dates on which such tax was actually withheld.

(l) If, on or before January thirty-first of the following taxable year, the taxpayer files a return for the taxable year and pays in full the amount computed on the return as payable, then no addition to tax shall be imposed under subsection (a) of this section with respect to any underpayment of the fourth required installment for the taxable year.

(m) For purposes of this section, if an individual is a farmer or fisherman for any taxable year, the following provisions shall apply: (1) There shall be only one required installment for the taxable year, (2) the due date for such installment shall be January fifteenth of the following taxable year, (3) the amount of such installment shall be equal to the lesser of (A) sixty-six and two-thirds per cent of the tax shown on the return for the taxable year, or, if no return is filed, sixty-six and two-thirds per cent of the tax for such year, or (B) if the preceding taxable year was a taxable year of twelve months and the individual filed a return for the preceding taxable year, one hundred per cent of the tax shown on the return for the preceding taxable year, (4) if, on or before March first of the following taxable year, the farmer or fisherman files a return and pays in full the amount computed on the return as payable, no addition to tax shall be imposed under subsection (a) of this section with respect to any underpayment of the required installment, as provided in subdivision (3) of this subsection, for the taxable year, and (5) an individual is a farmer or fisherman for any taxable year if such individual is a farmer or fisherman, as defined in Section 6654(i)(2) of the Internal Revenue Code, for the taxable year.

(n) (1) Except as otherwise provided in this subsection, this section shall apply to any trust or estate.

(2) With respect to any taxable year ending before the date two years after the date of the decedent's death, this section shall not apply to (A) the estate of such decedent, or (B) any trust (i) all of which was treated under Sections 671 to 679, inclusive, of the Internal Revenue Code as owned by the decedent and (ii) to which the residue of the decedent's estate will pass under his will or, if no will is admitted to probate, which is the trust primarily responsible for paying debts, taxes, and expenses of administration.

(3) In the case of any trust or estate to which this section applies, for any required installment, the annualized income installment is the excess, if any, of (A) an amount equal to the applicable percentage of the tax for the taxable year computed by placing on an annualized basis the Connecticut taxable income and the adjusted federal alternative minimum taxable income for months in the taxable year ending before the date one month before the due date for the installment, over (B) the aggregate amount of any prior required installments for the taxable year.

(June Sp. Sess. P.A. 91-3, S. 73, 168; May Sp. Sess. P.A. 92-5, S. 16, 17, 37; May Sp. Sess. P.A. 92-17, S. 15, 59; P.A. 93-74, S. 41, 67; 93-332, S. 16, 42; P.A. 95-26, S. 38, 52; 95-263, S. 2, 4; P.A. 97-81, S. 1, 2; 97-286, S. 5, 8; P.A. 04-201, S. 6.)

History: June Sp. Sess. P.A. 91-3, S. 73, effective August 22, 1991, and applicable to taxable years of taxpayers commencing on or after January 1, 1991; May Sp. Sess. P.A. 92-5 amended Subsec. (h) to make a technical change and added Subsec. (i), effective June 19, 1992, and applicable to taxable years of taxpayers commencing on or after January 1, 1992; May Sp. Sess. P.A. 92-17 amended Subsec. (b) to reduce the levels of estimated payments by 10% and to remove the minimum $50 penalty for nonpayment, effective June 19, 1992, and applicable to taxable years of taxpayers commencing on or after January 1, 1992; P.A. 93-74 replaced existing Subsec. (b) with new provisions to conform installment and estimated payments with the federal procedure, effective May 19, 1993, and applicable to taxable years commencing on and after January 1, 1993; P.A. 93-332 amended Subsec. (b)(5) to change statutory reference from Subdiv. (4) to Subdiv. (2), effective June 25, 1993, and applicable to taxable years commencing on or after January 1, 1993; P.A. 95-26 amended Subsec. (b)(4) to lower interest rate from 1.25% to 1% and made technical changes, effective July 1, 1995, and applicable to taxes due and owing on or after July 1, 1995, whether or not those taxes first became due before said date, but failed to take effect, since those provisions were deleted by subsequent act P.A. 95-263; P.A. 95-263 deleted Subsec. (a) re declaration requirement, added new Subsecs. (a) and (b) re interest on underpayment and the amount of underpayment, relettered and renumbered remaining Subsecs. and Subdivs. added reference to adjusted federal alternative minimum taxable income, and added Subsec. (j) re when no addition to tax is imposed, Subsec. (k) re tax withheld deemed payment of estimated tax, Subsec. (m) re installment payments by farmers and fishermen and Subsec. (n) re application of section to trusts and estates, effective July 6, 1995, and applicable to taxable years commencing on or after January 1, 1996; P.A. 97-81 amended Subsec. (j) to increase tax shown on return from $200 to $500, effective May 29, 1997, and applicable to taxable years commencing on or after January 1, 1997; P.A. 97-286 amended Subsec. (m) to require one installment instead of two and made conforming changes, effective June 26, 1997, and applicable to years commencing on or after January 1, 1997; P.A. 04-201 amended Subsec. (j)(1) to increase the minimum amount of tax for which additions to tax may be imposed from $500 or less to less than $1,000, effective June 3, 2004, and applicable to taxable years commencing on or after January 1, 2004.