REGEXVAULTv2.0
Finance/Tax & Registration
Verified Safe

Indian GSTIN (GST Identification Number) Regex for PHP

/^[0-3][0-9][A-Z]{5}[0-9]{4}[A-Z][1-9A-Z]Z[0-9A-Z]$/

What this pattern does

This page provides a well-structured, multi-part regular expression for matching indian gstin (gst identification number), 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
<?php
// Indian GSTIN (GST Identification Number)
// ReDoS-safe | RegexVault — Finance > Tax & Registration

define('INDIAN_GSTIN_GST_IDENTIFICATION_NUMBER_PATTERN', '/^[0-3][0-9][A-Z]{5}[0-9]{4}[A-Z][1-9A-Z]Z[0-9A-Z]$/');

function validate_indian_gstin_gst_identification_number(string $input): bool {
    return (bool) preg_match(INDIAN_GSTIN_GST_IDENTIFICATION_NUMBER_PATTERN, $input);
}

// Example
var_dump(validate_indian_gstin_gst_identification_number("27AAPFU0939F1ZV")); // bool(true)

Test Cases

Matches (Valid)
Rejects (Invalid)
27AAPFU0939F1ZVAAPFU0939F1ZV
29AABCR1718E1Z127aapfu0939f1zv
19AADCB2230M1Z027AAPFU0939F1Z
07AAACP0160H1Z940AAPFU0939F1ZV

When to use this pattern

This pattern is drawn from the Finance > Tax & Registration 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

GSTIN structure encodes the PAN (Personal Account Number) of the business owner — treat it as sensitive data. New UTs (like Ladakh, code 38) may require pattern updates.

Technical Notes

Structure: 2-digit state code (01-37) + 10-char PAN + 1 entity number + Z (default) + 1 checksum. State codes 01-37 (38 states/UTs). The 13th character is always Z. Checksum uses a modulus-based algorithm.

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