GSTIN Validator
Verify any GST number instantly — format check, checksum validation, and full decode of state, PAN, and entity type.
Structure
What the 15 characters of a GSTIN mean
27
State code
First 2 digits = state (27 = Maharashtra)
AABCF
PAN (alpha)
Chars 3–7: first 5 letters of PAN
8591
PAN (digits)
Chars 8–11: 4 digits of PAN
R
PAN check
Char 12: PAN check letter
1
Entity no.
Char 13: registration count in that state
Z
Default
Char 14: always Z for most registrations
5
Check digit
Char 15: computed checksum for validation
FAQ
Frequently asked questions
What is a GSTIN?+
GSTIN (Goods and Services Tax Identification Number) is a unique 15-character alphanumeric code assigned to every GST-registered business in India. It is required on tax invoices, credit notes, debit notes, and all GST returns. Without a valid GSTIN, a buyer cannot claim Input Tax Credit.
What does the GSTIN format mean?+
The 15 characters of a GSTIN encode: (1–2) State code (e.g. 27 = Maharashtra), (3–12) PAN of the business, (13) Entity number (1 = first registration, 2 = second, etc.), (14) "Z" by default, (15) Checksum digit for validation. This tool decodes all these fields for you.
How is the GSTIN checksum calculated?+
The checksum (15th character) is calculated using a weighted sum of the first 14 characters mapped to their position in the character set (0–9, A–Z = 0–35). Odd-position characters are weighted by 1, even-position by 2. The check digit is derived from 36 minus the sum modulo 36. Our validator performs this calculation automatically.
Can a GSTIN pass format validation but still be fake?+
Yes. A GSTIN that passes format and checksum validation is structurally correct, but it may belong to a cancelled or suspended registration. To verify if a GSTIN is currently active on the GST portal, check the official GST portal at www.gst.gov.in → Search Taxpayer. Our tool validates the structure and checksum only.
Is a GSTIN the same as a PAN?+
No, but a GSTIN contains the PAN. Characters 3–12 of the GSTIN are the PAN of the business owner or entity. A single PAN can have multiple GSTINs (one per state where the business is registered).
What is the entity number in a GSTIN?+
The 13th character of the GSTIN (1–9, then A–Z) indicates the registration count for that PAN in the same state. "1" means the first (and usually only) registration; "2" means a second registration in the same state under the same PAN (allowed for businesses with multiple verticals).
GSTIN auto-fill in the builder
Use a validated GSTIN in your invoice
Enter the GSTIN in ZapInvoice — the state code auto-fills and CGST/SGST/IGST splits automatically.
Create free GST invoice →