Conn. Gen. Stat. § 12-330i

(2) When it appears that any part of the deficiency for which a deficiency assessment is made is due to negligence or intentional disregard of the provisions of this chapter or regulations promulgated thereunder, there shall be imposed a penalty equal to ten per cent of the amount of such deficiency assessment, or fifty dollars, whichever is greater. When it appears that any part of the deficiency for which a deficiency assessment is made is due to fraud or intent to evade the provisions of this chapter or regulations promulgated thereunder, there shall be imposed a penalty equal to twenty-five per cent of the amount of such deficiency assessment.

(3) No taxpayer shall be subject to more than one penalty under this subsection in relation to the same tax period. The amount of any tax, penalty or interest due and unpaid under the provisions of this chapter may be collected under the provisions of section 12-35 . The warrant provided for under section 12-35 shall be signed by the commissioner or the commissioner's authorized agent. The amount of any such tax, penalty and interest shall be a lien, from the last day of the month next preceding the due date of such tax until discharged by payment, against all real estate of the taxpayer within the state, and a certificate of such lien signed by the commissioner may be filed for record in the office of the clerk of any town in which such real estate is situated, provided no such lien shall be effective as against any bona fide purchaser or qualified encumbrancer of any interest in any such property. When any tax with respect to which a lien has been recorded under the provisions of this section has been satisfied, the commissioner, upon request of any interested party, shall issue a certificate discharging such lien, which certificate shall be recorded in the same office in which the lien is recorded. Any action for the foreclosure of such lien shall be brought by the Attorney General in the name of the state in the superior court for the judicial district in which the property subject to such lien is situated, or, if such property is located in two or more judicial districts, in the superior court for any one such judicial district, and the court may limit the time for redemption or order the sale of such property or make such other or further decree as it judges equitable.

(b) Except in the case of a wilfully false or fraudulent return with intent to evade the tax, no assessment of additional tax with respect to any return shall be made after the expiration of more than three years from the date of the filing of such return or from the original due date of such return, whichever is later. If no return has been filed as provided in this chapter the commissioner may make such return at any time thereafter, according to the best information obtainable and according to the form prescribed. There shall be added to the tax imposed upon the basis of such return an amount equal to ten per cent of such tax, or fifty dollars, whichever is greater. The tax shall bear interest at the rate of one per cent per month or fraction thereof from the due date of such tax to the date of payment. If, prior to the expiration of the period prescribed in this section for the assessment of additional tax, a taxpayer has consented in writing that such period may be extended, the amount of such additional tax due may be determined at any time within such extended period. Any such extended period may be further extended by consent in writing before the expiration of such extended period.
payment. If, prior to the expiration of the period prescribed in this section for the assessment of additional tax, a taxpayer has consented in writing that such period may be extended, the amount of such additional tax due may be determined at any time within such extended period. Any such extended period may be further extended by consent in writing before the expiration of such extended period.

(c) If, upon request by the commissioner or the commissioner's authorized agent, a distributor or an unclassified importer fails to immediately produce or immediately provide electronic access to the records required under subsection (a) of this section, such distributor or importer shall be subject to a civil penalty of one thousand dollars per day until the date such records are produced or electronic access is provided to the commissioner. Subject to the provisions of section 12-3a , the commissioner may waive all or part of the penalty provided under this subsection when it is proven to the commissioner's satisfaction that the failure to immediately produce or immediately provide electronic access to such records was due to reasonable cause.