New York Consolidated Laws, Real Property Tax Law - RPT § 489-fffff. Conversion of property

1. Any recipient whose property is the subject of a certificate of eligibility pursuant to this title, and who converts square footage within such property from the residential and commercial uses authorized pursuant to this title where such conversion results in twenty-five per centum or less of the aggregate floor area of such property being used or held out for use as commercial, community facility or accessory use space, shall cease to be eligible for further exemption as of the last date to which such recipient proves by clear and convincing evidence that more than twenty-five per centum of the aggregate floor area of such property was used or held out for use as commercial, community facility or accessory use space, and shall pay, with interest, any taxes for which an exemption was claimed after such date, including the pro rata share of tax for which any exemption was claimed during the tax year in which twenty-five per centum or less of the aggregate floor area of such property was used or held out for use as commercial, community facility or accessory use space.

2. Any recipient whose property is the subject of a certificate of eligibility pursuant to this title, and who uses such property, or any portion of such property, for any restricted activity prior to the expiration of the benefit period, shall cease to be eligible for further exemption as of the last date to which such recipient proves by clear and convincing evidence that such property, or any portion of such property, was not used for any restricted activity.  Such recipient shall pay, with interest, any taxes for which an exemption was claimed after such date, including the pro rata share of tax for which any exemption was claimed during the tax year in which such use occurred.