Indian GSTIN (GST Identification Number) Regex for Python

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 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

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

import re

indian_gstin_gst_identification_number_pattern = re.compile(r'^[0-3][0-9][A-Z]{5}[0-9]{4}[A-Z][1-9A-Z]Z[0-9A-Z]$')

def validate_indian_gstin_gst_identification_number(value: str) -> bool:
    return bool(indian_gstin_gst_identification_number_pattern.fullmatch(value))

# Example
print(validate_indian_gstin_gst_identification_number("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 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

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.