GST Number Format: What Each Digit of a GSTIN Means
Last updated: 2 July 2026 · 5 min read
A GSTIN (Goods and Services Tax Identification Number) is a 15-character code that encodes the taxpayer's state, PAN and more. Understanding its structure helps you spot invalid numbers at a glance.
The 15 characters
| Position | Meaning |
|---|---|
| 1–2 | State code (e.g. 27 = Maharashtra) |
| 3–12 | PAN of the taxpayer (10 characters) |
| 13 | Entity number — how many registrations this PAN has in the state |
| 14 | Default letter, normally "Z" |
| 15 | Checksum character (mod-36) |
Example
In 27AAPFU0939F1ZV: 27 is Maharashtra, AAPFU0939F is the PAN, 1 is the first registration, Z is the default letter, and V is the checksum. The GSTIN validator recomputes that checksum to confirm the number is genuine — not just correctly patterned.
Why the checksum matters
A regex can confirm the shape of a GSTIN, but only the mod-36 checksum confirms the digits are internally consistent, catching typos. Remember: a valid checksum means the number is well-formed, not that the business is actively registered — check the GST portal for that.
FAQ
How many digits is a GSTIN?
15 characters: 2-digit state code, 10-character PAN, 13th entity digit, "Z", and a checksum character.
Related: GSTIN validator, state code list, PAN validator.