Conn. Gen. Stat. § 12-222

(b) Such return shall be due on or before the fifteenth day of the month next succeeding the due date of the company's corresponding federal income tax return for the income year, determined without regard to any extension of time for filing, or, in the case of any company that is not required to file a federal income tax return for the income year, on or before the fifteenth day of the fifth month next succeeding the end of the income year.

(c) The commissioner may grant a reasonable extension of time for filing a return, if the company files a tentative return and application for extension of time in which to file a return, on forms furnished or prescribed by the commissioner, and pays the tax reported to be due on such tentative return on or before the original due date of the return, as provided in subsection (b) of this section. Any additional tax which may be found to be due on the filing of the return as allowed by such extension shall bear interest at the rate of one per cent per month or fraction thereof from the original due date of the return to the date of actual payment. Notwithstanding the provisions of section 12-229 , if the commissioner grants a reasonable extension of time for filing a return, no penalty shall be imposed on account of any failure to pay the amount of tax reported to be due on a return within the time specified under the provisions of this chapter if the excess of the amount of tax shown on the return over the amount of tax paid on or before the original due date of such return is no greater than ten per cent of the amount of tax shown on such return, and any balance due shown on such return is remitted with such return on or before the extended due date of such return.

(d) In any case in which the commissioner believes that it would be advantageous for the computation of the tax as imposed by this part, such state return shall be accompanied by a true copy of the last income tax return, if any, made to the Internal Revenue Service.

(e) The amount of tax reported to be due on such return or tentative return shall be due and payable on or before the original due date of the return, as defined in subsection (b) of this section.

(f) Payment shall be made in cash or by check, draft or money order drawn to the order of the Commissioner of Revenue Services.

(g) (1) A combined group shall file a combined unitary tax return under this chapter in the form and manner prescribed by the Commissioner of Revenue Services. The designated taxable member of a combined group shall file the combined unitary tax return on behalf of the taxable members of the combined group and shall pay the tax on behalf of such taxable members. A designated taxable member shall not be liable to, and shall be entitled to recover a payment made pursuant to this subdivision from, the taxable member on whose behalf the payment was made.

(2) If a member of a combined group has a different income year than the group income year, such member with a different income year shall report amounts from its return for its income year that ends during the group income year, provided no such reporting of amounts shall be required of such member until its first income year beginning on or after January 1, 2016.

(3) Notwithstanding the provisions of subdivision (1) of this subsection, each taxable member of a combined group is jointly and severally liable for the tax due from any taxable member under this chapter, whether or not such tax has been self-assessed, and for any interest, penalties or additions to tax due from any taxable member under this chapter.
e year beginning on or after January 1, 2016.

(3) Notwithstanding the provisions of subdivision (1) of this subsection, each taxable member of a combined group is jointly and severally liable for the tax due from any taxable member under this chapter, whether or not such tax has been self-assessed, and for any interest, penalties or additions to tax due from any taxable member under this chapter.

(4) In all cases where a combined group is eligible to select the designated taxable member of the combined group, notice of the selection shall be submitted in written form to the commissioner not later than the due date, or, if an extension of time to file has been requested and granted, not later than the extended due date of the combined unitary tax return for the initial income year that such a return is required. The subsequent selection of another designated taxable member shall be subject to the approval of the commissioner.

(5) For purposes of this chapter, the designated taxable member is authorized to do the following acts on behalf of taxable and nontaxable members of the combined group, including, but not limited to: (A) Signing the combined unitary tax return, including any amendments to such return; (B) applying for extensions of time to file the return; (C) before the expiration of the time prescribed in section 12-233 for the examination of the return or the assessment of tax, consenting to an examination or assessment after such time and prior to the expiration of the period agreed upon; (D) making offers of compromise under section 12-2d ; (E) entering into closing agreements under section 12-2e ; and (F) receiving a refund or credit of a tax overpayment under this chapter.

(6) For purposes of this chapter, the commissioner may, at the commissioner's sole discretion: (A) Send any notice to either the designated taxable member or a taxable member or members of the combined group; (B) make any deficiency assessment against either the designated taxable member or a taxable member or members of the combined group; (C) refund or credit any overpayment to either the designated taxable member or a taxable member or members of the combined group; (D) require any payment to be made by electronic funds transfer; and (E) require the combined unitary tax return to be electronically filed.

Cited. 124 C. 406; 129 C. 664; 135 C. 61.

Cited. 44 CS 90; Id., 126.