GSTIN Number Format: What the 15 Characters of Your GST Number Mean

A GSTIN sits at the top of every tax invoice. Most people copy it into a form without reading it, but it tells you more than you might expect: the State of registration, the supplier's PAN, and whether the number was typed correctly.

This guide explains each part, what a format check can and cannot prove, and how to check a supplier's GSTIN before you rely on it for input tax credit.

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GSTIN and GSTN Are Not the Same Thing

When someone says "send me your GSTN", they almost always mean the GSTIN.

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The 15-Character Structure Under Rule 10

Rule 10(1) of the CGST Rules, 2017 says that when registration is approved, the certificate in Form GST REG-06 is made available on the common portal and a GSTIN is assigned with these characters:

That is all the rule itself prescribes. The finer meaning of positions 13 and 14 comes from how the GST portal issues numbers in practice, which is covered below.

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Positions 1 and 2: The State Code

The first two digits show the State or Union Territory of that registration, not the head office. A company registered in Telangana and Maharashtra holds two GSTINs, one starting with 36 and the other with 27.

State Code List

These codes are from the State Code Master on the official e-invoice portal (einvoice1.gst.gov.in).

The same master also lists 96 and 99 as "Other Countries", which are used for places outside India on e-invoices. Code 28 does not appear in the current master.

Why it matters: comparing the supplier's State code with the place of supply is the quickest way to check whether an invoice should carry CGST plus SGST (same State) or IGST (different States). For a Hyderabad business, a supplier GSTIN starting with 36 and a place of supply in Telangana means CGST plus SGST.

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Positions 3 to 12: The PAN (or TAN)

The next ten characters are normally the PAN of the registered person, in the usual PAN format of five letters, four digits and one letter.

If your PAN details are wrong, the GSTIN will carry the error too. Fix the PAN first; see our PAN application and correction guide.

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Positions 13 and 14: The Entity Code

Rule 10 calls these two characters the entity code and says nothing more. On GSTINs actually issued by the portal, they follow a consistent pattern:

Example: a business with a factory and a separately registered business vertical in Telangana may hold two GSTINs that both start with 36 and carry the same PAN, but end with 1Z and 2Z before the checksum. These are two separate registrations. Each files its own returns and has its own credit ledger. Separate registration for business verticals within a State is allowed under Section 25(2) of the CGST Act and Rule 11. Our guide to managing multiple GSTINs covers how to keep the books apart.

Do not treat "Z" as a hard rule. The 14th character is not fixed in Rule 10, and special registrations, such as TAN-based ones, may not follow the regular pattern. If a GSTIN looks unusual, check it on the portal rather than rejecting it on sight.

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Position 15: The Checksum

The last character is a checksum calculated from the first 14 characters. Its job is to catch typing mistakes. If one character in the first 14 is wrong or two characters are swapped, the checksum will almost always stop matching and the portal will reject the number.

What the checksum does not do: it only proves the string is well formed. It says nothing about whether the registration is active, or whether it belongs to the business that sent you the invoice.

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A Worked Example

The GSTIN below is made up for illustration, using the sample PAN ABCDE1234F.

36ABCDE1234F1Z1

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GSTIN Compared with Other Numbers

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What a Format Check Cannot Tell You

This matters for input tax credit. Under Section 16(2)(aa) of the CGST Act, you can claim credit only when the supplier has reported your invoice in their outward supply statement and it has been communicated to you, which in practice means it shows in your GSTR-2B. A supplier with a cancelled registration, or one who does not file GSTR-1, will not get your invoice into GSTR-2B. Our GSTR-2B reconciliation guide explains how to match your purchase register against it.

How to Check a GSTIN Before You Transact

Step-by-Step Guide

How to Verify a GSTIN

Format first, portal second

1

Read the Format

Check that it has 15 characters, a valid State code, the supplier's PAN in positions 3 to 12, and nothing obviously mistyped, such as the letter O in place of zero.

Format

2

Search on gst.gov.in

Go to Search Taxpayer, then Search by GSTIN/UIN, and enter the number. No login is needed.

Portal

3

Check Status and Names

Confirm the status is Active and that the legal name and trade name match the business you are dealing with.

Status

4

Look at Return Filing

Check the return filing details. A supplier who has stopped filing is a risk to your input tax credit.

Filing

5

Match the Address

Compare the principal place of business with the address on the invoice.

Address

6

Re-check Large Suppliers

A registration that was active when you onboarded a supplier can be cancelled later. Re-check high-value suppliers from time to time.

Re-check

Source: GST portal (gst.gov.in), Search Taxpayer

Common Typing Errors

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Quick Reference

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Where Tax Garden Helps

If you are about to register, see our step-by-step GST registration guide and the GST registration turnover limits. If you have already applied, you can check your ARN status on the portal.

Tax Garden's GST team can help with:

• New registration: getting your GSTIN through our GST registration service
• Additional States and verticals: separate registrations when you expand
• Supplier checks: confirming status and filing record for key suppliers before you claim credit
• ITC mismatches: working out why an invoice is missing from GSTR-2B

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Sources: Rule 10(1) and Rule 11, Central Goods and Services Tax Rules, 2017 (CBIC consolidated rules, cbic-gst.gov.in); Section 16(2)(aa) and Section 25(2), CGST Act, 2017; State Code Master, e-invoice portal (einvoice1.gst.gov.in); Search Taxpayer facility, gst.gov.in. The meaning of the 13th and 14th characters described here reflects how the portal issues GSTINs; it is not set out in Rule 10. This article is general information on the GSTIN format and not a substitute for professional advice.

Frequently Asked Questions

How many characters does a GSTIN have?

15. Rule 10(1) of the CGST Rules, 2017 sets the structure: two characters for the State code, ten characters for the PAN or TAN, two characters for the entity code, and one checksum character.

What is the difference between GSTIN and GSTN?

GSTIN is the Goods and Services Tax Identification Number, the 15-character number given to a registered person. GSTN is the Goods and Services Tax Network, the company that runs the GST portal. They are not the same thing.

What do the first two digits of a GSTIN mean?

They are the State or Union Territory code of that registration. For example, 36 is Telangana, 37 is Andhra Pradesh, 27 is Maharashtra, 29 is Karnataka and 07 is Delhi, as listed in the State Code Master on the official e-invoice portal.

Is the PAN part of the GSTIN?

Yes. Characters 3 to 12 are the Permanent Account Number of the registered person. Rule 10 also allows a Tax Deduction and Collection Account Number (TAN) in this place, which is used for registrations such as GST TDS deductors.

What do the 13th and 14th characters of a GSTIN mean?

Rule 10 only says they are a two-character entity code. On GSTINs issued through the portal, the 13th character is commonly a running number for registrations under the same PAN in that State, and the 14th is Z on regular taxpayer GSTINs. These are portal conventions, not written into the rule, so special registrations can differ.

What is the 15th character of a GSTIN?

It is a checksum character calculated from the first 14 characters. It helps catch typing mistakes. A GSTIN with a wrong checksum will be rejected by the GST portal.

Can one PAN have more than one GSTIN?

Yes. Registration is State-wise, so a business registered in several States gets one GSTIN per State, all carrying the same PAN. A business can also take separate registrations for business verticals within a State under Section 25(2) and Rule 11.

Does a correctly formatted GSTIN mean the supplier is genuine?

No. A format check only shows the number is well formed. Use Search Taxpayer on gst.gov.in to check that the registration is active, that the legal and trade names match your supplier, and how regularly returns are being filed.

How do I check if a GSTIN is active?

On gst.gov.in, go to Search Taxpayer, then Search by GSTIN/UIN, and enter the number. The result shows the legal name, trade name, registration status, date of registration and return filing details.