LEI Code Structure Explained: The 20 Characters of ISO 17442

Every LEI looks like a random jumble — take `5493001KJTIIGC8Y1R12`. It isn't random at all. The format is fixed by the international standard ISO 17442, and once you know how it's built, those 20 characters start to make sense.

The four parts of an LEI

Characters 1–4 — the LOU prefix. These identify the Local Operating Unit that issued the code. Every accredited issuer has its own prefix.
Characters 5–6 — reserved. Always set to "00", held in reserve by the standard.
Characters 7–18 — the entity identifier. A unique 12-character string assigned to your specific entity. This is what makes your LEI yours and no one else's.
Characters 19–20 — check digits. Two digits calculated from the rest of the code using a mod-97 formula (ISO/IEC 7064), purely to catch transcription errors.

Why the structure matters

The LOU prefix means two different issuers can never hand out the same code. The check digits mean a single mistyped character is detected instantly, before a bad code reaches a trade or a report.

An LEI carries no hidden meaning — no country code, no sector, no size. It's a neutral, permanent identifier. Even if your company changes its name or restructures, the LEI stays the same; only the reference data behind it is updated.

For the bigger picture, see What is an LEI code?, What is GLEIF? and What is an LOU?