US Employer Identification Number (EIN) Regex for Python

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 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

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

import re

us_employer_identification_number_ein_pattern = re.compile(r'^(?:0[1-9]|[1-9][0-9])-[0-9]{7}$')

def validate_us_employer_identification_number_ein(value: str) -> bool:
    return bool(us_employer_identification_number_ein_pattern.fullmatch(value))

# Example
print(validate_us_employer_identification_number_ein("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 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 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.