Conn. Gen. Stat. § 31-269: Refunds and deficiencies.

If more or less than the correct amount of contributions imposed has been paid with respect to employment during any period, the amount of the overpayment shall be refunded to the employer from the contribution account of the Unemployment Compensation Fund or the amount of the underpayment shall be paid by the employer to the administrator at such time as the administrator prescribes, provided no refund shall be made unless request has been made within three years from the due date of the contributions claimed to have been overpaid or which would be contrary to the requirements of the Social Security Act or any amendments thereto. Any refunds of interest paid into the Employment Security Special Administration Fund established by section 31-259 shall be paid from said fund. If the overstatement of wages results in unemployment compensation benefits being paid, the amount of any overpayment of unemployment compensation benefits shall be deducted from any refunds of contributions until the amount of overpayment of unemployment compensation benefits has been recovered.