Conn. Gen. Stat. § 12-71c

(b) Any person claiming a property tax credit with respect to a motor vehicle in accordance with subsection (a) of this section shall file with the assessor in the town in which such person is entitled to such property tax credit, documentation satisfactory to the assessor concerning the sale, total damage, theft or removal and registration of such motor vehicle. Such documentation shall be filed not later than the thirty-first day of December immediately following the end of the assessment year which next follows the assessment year in which such motor vehicle was sold, damaged, stolen or removed and registered. Failure to file such claim and documentation as prescribed herein shall constitute a waiver of the right to such property tax credit.