Conn. Gen. Stat. § 12-415

(b) Interest. The amount of the assessment or reassessment, exclusive of penalties, shall bear interest at the rate of one per cent per month or fraction thereof from the last day of the month succeeding the period for which the amount or any portion thereof should have been returned until the date of payment.

(c) Deficiency due to negligence or intentional disregard. When it appears that any part of the deficiency for which a deficiency assessment or reassessment 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 fifteen per cent of the amount of such deficiency assessment or reassessment, or fifty dollars, whichever is greater.

(d) Deficiency due to fraud or intent to evade. When it appears that any part of the deficiency for which a deficiency assessment or reassessment 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 or reassessment. No taxpayer shall be subject to a penalty under both subsection (c) of this section and this subsection in relation to the same tax period.

(e) Notice of assessment or reassessment. The commissioner shall give to the retailer or person storing, accepting, consuming or otherwise using services or tangible personal property written notice of the commissioner's assessment or reassessment. The notice may be served personally or by mail. If by mail, it shall be addressed to the retailer or person storing, accepting, consuming or otherwise using services or tangible personal property at the address as it appears in the records of the commissioner's office.

(f) Limitations on deficiency assessment or reassessment. Except in the case of fraud, intent to evade this chapter or authorized regulations, failure to make a return, or claim for additional amount pursuant to subsection (c) of section 12-418 , every notice of a deficiency assessment or reassessment shall be mailed within three years after the last day of the month following the period for which the amount is proposed to be assessed or reassessed or within three years after the return is filed, whichever period expires later. The limitation specified in this subsection does not apply in case of a sales tax proposed to be assessed or reassessed with respect to sales of services or property for the storage, acceptance, consumption or other use of which notice of a deficiency assessment or reassessment has been or is given pursuant to this subsection, subsection (e) of this section, subsection (c) of section 12-416 , and subsection (a) of section 12-417 . The limitation specified in this subsection does not apply in case of an amount of use tax proposed to be assessed or reassessed with respect to storage, acceptance, consumption or other use of services or property for the sale of which notice of a deficiency assessment or reassessment has been or is given pursuant to this subsection and said subsections.

(g) Waiver. If, before the expiration of the time prescribed in subsection (f) of this section for the mailing of a notice of deficiency assessment or reassessment, the taxpayer has consented in writing to the mailing of the notice after such time, the notice may be mailed at any time prior to the expiration of the period agreed upon. The period so agreed upon may be extended by subsequent agreements in writing made before the expiration of the period previously agreed upon.

Cited. 168 C. 597; 187 C. 581; 210 C. 401; 231 C. 315; 235 C. 393. Section does not require proof of intent to evade “sales tax”; it requires proof of intent to evade the Sales and Use Taxes Act or authorized regulations, which laws require accurate reporting and record keeping. 264 C. 286.

Cited. 12 CA 417; 43 CA 744.

Cited. 31 CS 373; 44 CS 297.