Canadian Business Number (BN) Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching canadian business number (bn), 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

# Canadian Business Number (BN)
# ReDoS-safe | RegexVault — Finance > Tax & Registration

import re

canadian_business_number_bn_pattern = re.compile(r'^[0-9]{9}(?:[A-Z]{2}[0-9]{4})?$')

def validate_canadian_business_number_bn(value: str) -> bool:
    return bool(canadian_business_number_bn_pattern.fullmatch(value))

# Example
print(validate_canadian_business_number_bn("123456789"))  # 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 9-digit root identifies the business. Program identifiers: RT (GST/HST), RP (payroll), RC (corporate income tax), RZ (information returns). The 4-digit reference number distinguishes multiple accounts of the same type.