(i) The extent of such exemption shall be decreased by ten per centum of the "exemption base" each year during such additional period. The "exemption base" shall be the increase in assessed value as determined in the initial year of the term of the exemption, except as provided in subparagraph (ii) of this paragraph.

(ii) In any year in which a change in level of assessment of fifteen percent or more is certified for a final assessment roll pursuant to the rules of the commissioner, the exemption base shall be multiplied by a fraction, the numerator of which shall be the total assessed value of the parcel on such final assessment roll (after accounting for any physical or quantity changes to the parcel since the immediately preceding assessment roll), and the denominator of which shall be the total assessed value of the parcel on the immediately preceding final assessment roll. The result shall be the new exemption base. The exemption shall thereupon be recomputed to take into account the new exemption base, notwithstanding the fact that the assessor receives certification of the change in level of assessment after the completion, verification and filing of the final assessment roll. In the event the assessor does not have custody of the roll when such certification is received, the assessor shall certify the recomputed exemption to the local officers having custody and control of the roll, and such local officers are hereby directed and authorized to enter the recomputed exemption certified by the assessor on the roll. The assessor shall give written notice of such recomputed exemption to the property owner, who may, if he or she believes that the exemption was recomputed incorrectly, apply for a correction in the manner provided by title three of article five of this chapter for the correction of clerical errors.

(b) No such exemption shall be granted for reconstruction or rehabilitation unless such reconstruction or rehabilitation was commenced subsequent to the effective date of the local law or resolution adopted pursuant to subdivision one of this section; provided, however, that such local law or resolution may provide that such reconstruction or rehabilitation commenced prior to the effective date of such local law or resolution may qualify for the exemption.

(c) No such exemption shall be granted to an historic barn which is receiving an exemption pursuant to section four hundred eighty-three of this title or which has received an exemption pursuant to that section within ten years of the date of the application for exemption filed pursuant to this section.

(d) No such exemption shall be granted to an historic barn which is used for residential purposes.

(e) No such exemption shall be granted for reconstruction and rehabilitation expenses that materially alter the historic appearance of the barn. 3. Such exemption shall be granted only upon application by the owner of such barn on a form prescribed by the commissioner. The application shall be filed with the assessor of the city, town, village or county having the power to assess property for taxation on or before the appropriate taxable status date of such city, town, village or county. 4. If satisfied that the barn is entitled to an exemption pursuant to this section, the assessor shall approve the application and such barn shall thereafter be exempt from taxation as herein provided commencing with the assessment roll prepared on the basis of the taxable status date referred to in subdivision three of this section. The assessed value of any exemption granted pursuant to this section shall be entered by the assessor on the assessment roll with the taxable property, with the amount of the exemption shown in a separate column. 5. For the purposes of this section, an historic barn shall mean a structure that was at least partially constructed before nineteen hundred thirty-six and that was originally designed and used for storing farm equipment or agricultural products, or for housing livestock. * NB Applies to taxable years beginning on or after January 1, 1997