Definition
The Unique Entity Identifier (UEI) is a 12-character alphanumeric code that uniquely identifies a business entity for federal contracting purposes. It replaced the DUNS number in April 2022 as the official identifier for SAM.gov registration. The UEI is automatically assigned when you complete your SAM.gov entity registration and is required for all federal contracts, grants, and assistance programs.
Official Source
SAM.gov