IBAN (UK — GB) Regex for PHP

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching iban (uk — gb), ported and verified for PHP. 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 PHP project — whether you're validating in a Laravel validator, a WordPress plugin, or a standalone PHP script.

Php Implementation

<?php
// IBAN (UK — GB)
// ReDoS-safe | RegexVault — Finance > Bank Identifiers

define('IBAN_UK_GB_PATTERN', '/^GB[0-9]{2}[A-Z]{4}[0-9]{14}$/');

function validate_iban_uk_gb(string $input): bool {
    return (bool) preg_match(IBAN_UK_GB_PATTERN, $input);
}

// Example
var_dump(validate_iban_uk_gb("GB29NWBK60161331926819")); // bool(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 PHP developers because especially relevant in PHP where PCRE backtracking limits can trigger silent failures on malicious input. 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.