How to validate a GST number
- Type or paste a GSTIN — spaces and lowercase letters are fine.
- See straight away whether it's valid, with the state, PAN, taxpayer type and check digit explained.
- To check a list, paste a column from Excel or your accounting software, then download the results as a CSV.
GSTIN structure
| Characters | Meaning | Example (27AAPFU0939F1ZV) |
|---|---|---|
| 1–2 | State code | 27 = Maharashtra |
| 3–12 | PAN of the business | AAPFU0939F (4th letter F = firm) |
| 13 | Registration number for that PAN in the state | 1 = first registration |
| 14 | Default letter | Z |
| 15 | Check digit | V |
When to check a GSTIN
- Before raising an invoice: a wrong buyer GSTIN means they can't claim input tax credit, and you'll have to amend your GSTR-1.
- Vendor onboarding: validate a supplier master in bulk before importing it into Tally or your ERP.
- Place of supply: the state code tells you whether to charge IGST (different state) or CGST + SGST (same state).
Everything runs in your browser — the numbers you paste aren't uploaded. Create a GST invoice with the invoice generator (it checks GSTINs as you type), or work out tax with the GST calculator.
Frequently asked questions
What is the format of a GST number?
A GSTIN has 15 characters: a 2-digit state code, the business's 10-character PAN, a registration number (1–9 or A–Z) for that PAN in the state, the letter Z, and a check digit calculated from the first 14 characters.
Does a valid result mean the GSTIN is active?
No. This tool confirms the number is correctly formed — a typo almost always breaks the check digit. To see whether a GSTIN is registered, active or cancelled, and the legal name, search it on the official GST portal (gst.gov.in → Search Taxpayer).
How is the GSTIN check digit calculated?
Each of the first 14 characters is converted to a number (0–9, then A=10 to Z=35) and multiplied alternately by 1 and 2. For each product, the quotient and remainder after dividing by 36 are added up. The check digit is the character for (36 − total mod 36) mod 36.
Can I check many GST numbers at once?
Yes. Paste a column from Excel or a list separated by lines, commas or spaces — up to 5,000 at a time. You'll get a table of results and can download them as a CSV or copy just the valid GSTINs.
What does the 13th character mean?
It counts registrations for the same PAN in the same state: 1 for the first, 2 for a second business vertical, and so on, continuing with letters after 9.
Last updated: 24 September 2026Suggest an improvement · Report a problem