US Employer Identification Number (EIN) Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching us employer identification number (ein), 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

// US Employer Identification Number (EIN)
// ReDoS-safe | RegexVault — Finance > Tax & Registration

const usEmployerIdentificationNumberEinRegex = /^(?:0[1-9]|[1-9][0-9])-[0-9]{7}$/;

function validateUsEmployerIdentificationNumberEin(input: string): boolean {
  return usEmployerIdentificationNumberEinRegex.test(input);
}

// Example
console.log(validateUsEmployerIdentificationNumberEin("12-3456789")); // 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 two digits identify the IRS campus that issued the EIN. 00 is not a valid prefix. EINs are the business equivalent of SSNs. Used on W-2, 1099, and other tax forms.