Legal Entity Identifier (LEI) Regex for Python

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching legal entity identifier (lei), ported and verified for Python. Financial data validation has zero tolerance for false negatives — a missed invalid entry can corrupt downstream calculations. The snippet below is ready to drop into your Python project — whether you're validating in a Django view, a FastAPI endpoint, or a standalone data processing script.

Python Implementation

# Legal Entity Identifier (LEI)
# ReDoS-safe | RegexVault — Finance > Tax & Registration

import re

legal_entity_identifier_lei_pattern = re.compile(r'^[A-Z0-9]{18}[0-9]{2}$')

def validate_legal_entity_identifier_lei(value: str) -> bool:
    return bool(legal_entity_identifier_lei_pattern.fullmatch(value))

# Example
print(validate_legal_entity_identifier_lei("7H6GLXDRUGQFU57RNE97"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Finance > Tax & Registration category and carries a ReDoS-safe certification. That matters for Python developers because particularly important in Python web servers where CPU-bound regex operations can stall concurrent request handling. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

The first 4 characters identify the LOU (Local Operating Unit). Characters 5-18 are the entity-specific portion. The last 2 digits are check digits per ISO 17442 (MOD-97-10). Required by MiFID II and other regulations for financial reporting.