Australian BSB (Bank-State-Branch) Regex for Python

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching australian bsb (bank-state-branch), 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

# Australian BSB (Bank-State-Branch)
# ReDoS-safe | RegexVault — Finance > Bank Identifiers

import re

australian_bsb_bankstatebranch_pattern = re.compile(r'^[0-9]{3}-?[0-9]{3}$')

def validate_australian_bsb_bankstatebranch(value: str) -> bool:
    return bool(australian_bsb_bankstatebranch_pattern.fullmatch(value))

# Example
print(validate_australian_bsb_bankstatebranch("062-000"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Finance > Bank Identifiers 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

First digit identifies the financial institution (0=ANZ, 1=WBC/STV, 2=CBA, 3=NAB, 6=CUSCAL/regionals). Second digit is the state. Validate against APCA's BSB directory for active accounts.