GSTIN Validator & State Code Decoder
Check whether a GSTIN is correctly formed, and decode what it tells you — the state, the PAN behind it, and the type of entity. Runs entirely in your browser.
Checked entirely in your browser — the number is not sent anywhere.
How a GSTIN is built
- 1–2
- State code
- 3–12
- PAN of the business
- 13
- Registration number for that PAN in that state
- 14
- Always Z
- 15
- Check character
Result
Enter a GSTIN above to check its structure, state code and check character.
What the number encodes
A GSTIN is not an arbitrary identifier. It carries real information: where the business is registered, the PAN it belongs to, what kind of entity it is, and whether this is their first registration in that state or a subsequent one. Reading it tells you something useful before you ever look the business up.
The fourth character of the embedded PAN is particularly informative. A "C" means you are dealing with a company, "P" an individual or proprietor, "F" a firm or LLP, and "T" a trust. If a supposed private limited company gives you a GSTIN with a "P" in that position, something does not add up.
What a checksum can and cannot prove
The check character makes the number self-verifying. A single mistyped digit will almost always break it, and a randomly invented fifteen-character string has roughly a one in thirty-six chance of passing. That makes this an effective first filter.
It is not proof of registration. Someone could construct a structurally valid GSTIN that was never issued, and a genuine GSTIN may since have been cancelled or suspended. For anything that matters commercially — a large first order, or a supplier you are relying on for input tax credit — confirm against the GST portal, which checks live status rather than arithmetic.
Why this matters for input tax credit
Your customer claims credit for the tax you charge, and that claim is matched against what you report. If the GSTIN on the invoice is wrong, the invoice will not appear in their credit statement and they will come back to you to amend it. Catching the error before the invoice goes out costs nothing; catching it after a return has been filed costs an amendment and a difficult conversation.
Frequently asked questions
- What does each part of a GSTIN mean?
- A GSTIN is 15 characters. The first two are the state code, the next ten are the business's PAN, the thirteenth is the registration number for that PAN within that state, the fourteenth is always Z, and the fifteenth is a check character calculated from the rest.
- How does the check character work?
- It is a weighted modulo-36 checksum over the first fourteen characters, the same principle as the Luhn check on a card number but extended across letters as well as digits. Change any single character and the check no longer matches, which catches almost every typo and most invented numbers.
- Does a valid result mean the business is genuinely registered?
- No. This tool confirms the number is correctly formed — right structure, real state code, matching checksum. It cannot confirm that the GSTIN was actually issued, that the business is active, or that the trade name matches. For that you need the official GST portal's search, which queries live registration data.
- Why does the state code matter on an invoice?
- It decides whether you charge CGST and SGST or IGST. If your customer's state code differs from yours, the supply is inter-state and the whole tax goes as IGST. Getting this wrong is one of the most common reasons a customer's input tax credit gets held up.
- Why are some state codes missing?
- Codes 25 and 28 were retired. Daman & Diu merged with Dadra & Nagar Haveli into code 26 in January 2020, and undivided Andhra Pradesh's code 28 was replaced by 37 after Telangana was formed and given code 36. Ladakh was added as 38 in 2019.
- Can one business have more than one GSTIN?
- Yes. Registration is state-wise, so a business operating in five states has five GSTINs — all sharing the same PAN in positions 3 to 12, but with different state codes. The thirteenth character distinguishes multiple registrations by the same PAN within a single state.
Related free tools
- GST Calculator
Add or remove GST at the 2026 rates and see the CGST, SGST and IGST split instantly. Free, no sign-up.
- GST Invoice Generator
Create a GST-compliant tax invoice and download it as a PDF in under a minute. No sign-up, no watermark.
Read next
Checking client GSTINs one at a time?
A typo in a client's GSTIN surfaces months later, when their accountant cannot find your invoice in their credit. Smart Dhandha stores GSTINs against each client, applies the right CGST/SGST or IGST split from the place of supply, and keeps the whole billing history in one place.
- Client GSTINs stored once and reused
- Tax split chosen from the place of supply
- Invoices, payments and filing data together
This tool is provided free for general guidance and uses the rates noted above. Statutory rates change, and individual circumstances differ — please confirm with your accountant or a qualified professional before relying on these figures for filing or payroll.