The Unique Building Identifier file is designed to capture the complete inventory of multifamily buildings on which funds from subsidized housing programs have been spent. This file is intended to capture all multifamily units ever subsidized by either HOME or LIHTC, without duplication. The buildings in the file are unique according to their address and are identified by a key variable based on the building’s location, the programs under which the building has received subsidy, and date on which the subsidy began. This data set has been requested by organizations interested in preservation of the affordable housing stock, and should be useful to researchers both Federal and non-Federal.