Conn. Gen. Stat. § 12-89a: Certain organizations may be required by assessor to submit evidence of exemption from federal income tax.

Any organization claiming exemption from property tax in any municipality in which real or personal property belonging to such organization is situated, which exemption is claimed with respect to all or a portion of such property under the provisions of any of the subdivisions (7), (8), (10), (11), (12), (13), (14), (15), (16), (18), (27), (29), (49) or (58) of section 12-81, may be required upon request, at any time, by the assessor or board of assessors in such municipality to submit evidence of certification from the Internal Revenue Service, effective at the time of such request and in whatever form is then in use under Internal Revenue Service procedure for purposes of such certification, that such organization has been approved for exemption from federal income tax as an exempt organization under Section 501(c) or 501(d) of the Internal Revenue Code.