Conn. Agencies Regs. § 12-426-24
Every seller whose total liability for sales and use taxes for the twelve-month period ended on the preceding September thirtieth was less than one thousand dollars may, subject to the provisions of this section, be allowed to file tax returns and to pay the taxes reported thereon on an annual basis. The annual tax return shall be filed, and the sales and use taxes reported thereon shall be paid, on or before the last day of the month next succeeding the end of the seller's tax year. "Tax year" means the calendar year, or, in the discretion of the commissioner and at the request of the seller, any other period of twelve consecutive calendar months ending on the last day of a month other than December. Annual tax returns and annual payments of taxes will be allowed only after the submission of satisfactory statements or evidence by the seller that the seller's annual liability for sales and use taxes will not equal or exceed one thousand dollars and that the collection of taxes will not be jeopardized.
Conn. Agencies Regs. § 12-426-24