GSTIN validator: check a number before it goes on an invoice
A GSTIN is fifteen characters with a fixed internal structure and a check digit, which means a mistyped number can be detected without asking anyone. That check is worth running before you invoice, because the cost of a wrong GSTIN does not land on the vendor who supplied it — it lands on your customer. Their input tax credit is blocked, they query it with their accountant, and it comes back to you as a correction request weeks later. The validator checks the structure, decodes every part of it, and verifies the check digit, entirely in your browser.
Frequently asked questions
What does the GSTIN format consist of?
A 15-character GSTIN consists of: 2 digits for state code, 10 alphanumeric characters for PAN, 1 character for entity number, "Z" by default, and 1 check digit.
How do I read the GSTIN breakdown?
For example 27AAPFU0939F1ZV: 27 = Maharashtra state code, AAPFU0939F = PAN, 1 = entity number (first registration), Z = default letter, V = check digit. The validator decodes all of this for you instantly.
What happens if the checksum fails?
The tool checks the Mod-36 checksum, which is the final character derived from the first 14 characters. If it fails, the GSTIN is very likely a typo or an invalid number, even if it looks structurally correct.
Does the validator tell me the business type?
Yes. The character after the PAN indicates the entity type: for example different letters map to regular taxpayer, branch, GST practitioner, etc. The tool surfaces this alongside the state and PAN.
Why is it important to validate GSTIN before invoicing?
Invoicing an invalid GSTIN can cause your ITC claims to be rejected and can invite notices. Validating first protects your input tax credit and avoids compliance errors.
Can this tool check the real-time validity and status of a GSTIN?
This tool validates the structure and checksum offline. For live status — such as cancelled or suspended GSTINs — always cross-check on the official GST portal (gst.gov.in).
I found a GSTIN that fails validation. What should I do next?
Re-type the number carefully — failures are usually typos. If it still fails, request the correct GSTIN from the vendor, and if needed email rautprajwal36@gmail.com for help reading the number.