The Unique IPA Identifier (UII) is a 5-digit ID for the Certified Public Accountant (CPA) firm as a whole. If the CPA firm has previously done work with the HUD Real Estate Assessment Center (REAC), they may already have a UII. It is associated with the CPA firm's tax ID number and zip code.
To register for a UII, see IPA Registration and Assignment Instructions on the LEAP Information web page at: https://www.hud.gov/program_offices/housing/sfh/lender/SFH_Lenders_LEAP