What is an LEI?

A Legal Entity Identifier (LEI) is a 20-character alphanumeric code, defined by the ISO 17442 standard, that uniquely and permanently identifies a legally distinct entity taking part in financial transactions. One entity has exactly one LEI, and it never changes hands or gets reassigned.

The code itself is opaque, but it has structure: characters 1–4 identify the organisation that issued it (the LOU), characters 5–6 are reserved, characters 7–18 are specific to the entity, and characters 19–20 are check digits that let software validate the code. The meaning lives in the reference data published alongside it, not in the characters.

That reference data — legal name, legal form, registered address, registration authority, status and ownership — is maintained by the Global Legal Entity Identifier Foundation (GLEIF) and published as open data. LEIatlas turns each record into a page and, uniquely, keeps a history of how it changes over time.

LEIs exist because after the 2008 financial crisis, regulators found they could not reliably tell which legal entities were counterparties to which trades. A single global identifier fixes that, which is why an LEI is now mandatory for many kinds of regulated financial reporting.