Legal Entity Identifier (LEI) Regex for JavaScript

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching legal entity identifier (lei), ported and verified for JavaScript. 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 JavaScript project — whether you're validating in an Express middleware, a Next.js API route, or a client-side form.

Javascript Implementation

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

const legalEntityIdentifierLeiRegex = /^[A-Z0-9]{18}[0-9]{2}$/;

function validateLegalEntityIdentifierLei(input: string): boolean {
  return legalEntityIdentifierLeiRegex.test(input);
}

// Example
console.log(validateLegalEntityIdentifierLei("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 JavaScript developers because especially critical in long-running Node.js event loops where a ReDoS vulnerability can block the entire process. 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.