Conn. Gen. Stat. § 12-44: Penalty addition by certain municipal associations.

Twenty-five per cent of the amount of the valuation of any property taxable by any city, borough, school district, fire district or other municipal association which bases its grand list upon that of the town in which it is situated shall be added to such amount on the assessment list of such municipal association in each case in which twenty-five per cent has been added to such amount by such town for the failure to file a list as prescribed by section 12-41 or 12-43; but such penalty shall not be in addition to that previously imposed in the town assessment.