Indian GSTIN (GST Identification Number) Regex for JavaScript

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 JavaScript. 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 JavaScript project — whether you're validating in an Express middleware, a Next.js API route, or a client-side form.

Javascript Implementation

// Indian GSTIN (GST Identification Number)
// ReDoS-safe | RegexVault — Finance > Tax & Registration

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

function validateIndianGstinGstIdentificationNumber(input: string): boolean {
  return indianGstinGstIdentificationNumberRegex.test(input);
}

// Example
console.log(validateIndianGstinGstIdentificationNumber("27AAPFU0939F1ZV")); // 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 JavaScript developers because especially critical in long-running Node.js event loops where a ReDoS vulnerability can block the entire process. 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

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.