Free tool

GSTIN validator

Catch a mistyped GST number before it goes on a bill: check the 15-character pattern, the State code, the PAN inside it and the check character.

Runs in your browser. Nothing you type is sent to billinginfo.

How a GSTIN is built

Characters	What they are
1–2	State or UT code, e.g. 27 Maharashtra, 29 Karnataka, 07 Delhi
3–12	The PAN of the business; its 4th letter shows the type (P individual, C company, F firm or LLP, H HUF …)
13	Registration number for that PAN in that State: 1 for the first, 2 for the second, then letters
14	Usually Z
15	Check character, worked out from the first 14

The check character

Each of the first 14 characters is turned into a number (0–9, then A = 10 to Z = 35). Alternate characters are multiplied by 1 and 2; each product is split into its quotient and remainder by 36 and the two are added up. The check character is the one that brings the total to a multiple of 36. A single mistyped character, or two neighbours swapped, almost always breaks it, which is why this check catches typing mistakes.

What this check can’t tell you

A GSTIN can pass every check and still not be registered, or be cancelled or suspended. To confirm that a number is active and see the legal name, use “Search Taxpayer” on the GST portal, or GSTIN autofill in the billinginfo app (paid plans), which fetches the party’s details from the portal.

FAQ

Questions, answered.

Something else on your mind? Write to us or see the help page.

Is a valid check digit proof that the GSTIN exists?

No. It only proves the number is well-formed. Check its status on the GST portal before you claim input tax credit on a supplier’s invoice.

What does a 13th character of 2 mean?

The business has a second registration in that State under the same PAN, for example a separate business vertical.

Is my GSTIN sent anywhere?

No. The check runs in your browser.

Sources

Last checked on 2 November 2026. GST rules change through notifications and circulars; if something here looks out of date, please tell us. This page explains the rules in plain words and is not legal or tax advice.