N.Y. RPT Law § 489-FFFFF

§ 489-fffff. Conversion of property. 1. Any recipient whose property\nis the subject of a certificate of eligibility pursuant to this title,\nand who converts square footage within such property from the\nresidential and commercial uses authorized pursuant to this title where\nsuch conversion results in twenty-five per centum or less of the\naggregate floor area of such property being used or held out for use as\ncommercial, community facility or accessory use space, shall cease to be\neligible for further exemption as of the last date to which such\nrecipient proves by clear and convincing evidence that more than\ntwenty-five per centum of the aggregate floor area of such property was\nused or held out for use as commercial, community facility or accessory\nuse space, and shall pay, with interest, any taxes for which an\nexemption was claimed after such date, including the pro rata share of\ntax for which any exemption was claimed during the tax year in which\ntwenty-five per centum or less of the aggregate floor area of such\nproperty was used or held out for use as commercial, community facility\nor accessory use space.\n 2. Any recipient whose property is the subject of a certificate of\neligibility pursuant to this title, and who uses such property, or any\nportion of such property, for any restricted activity prior to the\nexpiration of the benefit period, shall cease to be eligible for further\nexemption as of the last date to which such recipient proves by clear\nand convincing evidence that such property, or any portion of such\nproperty, was not used for any restricted activity. Such recipient\nshall pay, with interest, any taxes for which an exemption was claimed\nafter such date, including the pro rata share of tax for which any\nexemption was claimed during the tax year in which such use occurred.\n