IBAN (UK — GB) Regex for Python

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching iban (uk — gb), 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

# IBAN (UK — GB)
# ReDoS-safe | RegexVault — Finance > Bank Identifiers

import re

iban_uk_gb_pattern = re.compile(r'^GB[0-9]{2}[A-Z]{4}[0-9]{14}$')

def validate_iban_uk_gb(value: str) -> bool:
    return bool(iban_uk_gb_pattern.fullmatch(value))

# Example
print(validate_iban_uk_gb("GB29NWBK60161331926819"))  # 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

UK IBANs are always 22 characters. The 4-char bank code is a subset of the BIC. UK personal accounts typically have 8-digit account numbers. Building society accounts may differ.