Conn. Gen. Stat. § 12-63k

(1) “Average increase in assessed value” means, for the assessment years commencing October 1, 2012, October 1, 2013, and October 1, 2014, the average of the increase in assessed value of commercial and industrial property, and personal property used exclusively for commercial or industrial purposes;

(2) “Base year” means the assessment year commencing October 1, 2014;

(3) “Increase from the base year” means the assessed value of commercial or industrial property for the current assessment year plus the current assessment year assessed value of any personal property acquired after the base year to be used exclusively for commercial or industrial purposes, less the assessed value of the commercial or industrial property for the base year;

(4) “Improvement to commercial or industrial property” or “improvement” includes, but is not limited to, any personal property acquired after the base year and used exclusively for commercial or industrial purposes; and

(5) “Mill rate” means the mill rate on real property and personal property other than motor vehicles.

(b) (1) Notwithstanding any provision of the general statutes or any special act, charter or home rule ordinance, a municipality that contains an enterprise zone designated pursuant to section 32-70 may, by vote of its legislative body, or in a municipality where the legislative body is a town meeting, by vote of the board of selectmen, provide that, for improvements to commercial or industrial property that result in an increase from the base year, (A) the assessment of such improvement shall be reduced as provided in subparagraph (B) of subdivision (2) of this subsection, and (B) the increase in tax revenue attributable to such improvement shall be allocated to reduce the assessments and total tax imposed on commercial and industrial properties located within the municipality as provided in subparagraph (C) of subdivision (2) of this subsection. The reduced assessments and allocations shall continue until the earlier of (i) the assessment year in which the mill rate for the municipality is not more than ten per cent greater than the average regional mill rate calculated pursuant to subdivision (2) of this subsection, or (ii) a date determined by such vote of the legislative body or the board of selectmen.

(2) (A) The tax collector of any municipality that has voted to reduce assessments pursuant to subdivision (1) of this subsection shall annually calculate the average regional mill rate based on the average mill rate of the planning region of the state, as designated under the provisions of section 16a-4a , in which the municipality is located.

(B) With respect to an improvement to commercial or industrial property that results in an increase from the base year of at least ten thousand dollars, the assessor of such municipality shall annually (i) determine the amount of the current assessment year increase in assessed value of the property that exceeds the average increase in assessed value with respect to the property, and (ii) reduce the assessment of the amount determined under clause (i) of this subparagraph to an amount that yields a total tax on such amount equal to the tax that would be imposed at the applicable average regional mill rate.
ne the amount of the current assessment year increase in assessed value of the property that exceeds the average increase in assessed value with respect to the property, and (ii) reduce the assessment of the amount determined under clause (i) of this subparagraph to an amount that yields a total tax on such amount equal to the tax that would be imposed at the applicable average regional mill rate.

(C) Each such municipality shall allocate tax revenue attributable to such improvements to reduce the assessments and total tax imposed on each commercial and industrial property located within the municipality, or located within the neighborhood revitalization zone in which the improved property is located, that is not subject to any other form of property tax relief and that has a total assessment of less than fifteen million dollars, except that such municipality may retain the amount equal to the average increase in assessed value on such commercial and industrial properties, and may retain an additional twenty per cent of the current assessment year increase in assessed value that is in excess of the average increase in assessed value.

(c) The assessor of any municipality that has voted to reduce assessments pursuant to subdivision (1) of subsection (b) of this section shall calculate assessed values under this section without regard to any revaluation of real property that takes place on or after the date of such vote.