J-51

J-51 was the city's long-running renovation benefit: exemptions and abatements for qualifying rehabilitation and conversion work in residential buildings, with regulation of units during benefit periods as a signature condition. The program lapsed and was revived in successor form with narrowed eligibility, continuing the same rehabilitation-for-benefits logic.

Its analytical afterlife is substantial: decades of buildings took J-51 benefits, and the regulation obligation during benefit periods generated consequential litigation — units deregulated while benefits ran were improperly deregulated, with overcharge exposure that survives today. A building's J-51 history is therefore both a tax fact and a rent-regulation fact, and the two must be read together.