GST & Tax Tools

GSTIN Format Checker

Validate the structural format and 15th-character Luhn-modulo-36 checksum of any Indian GST Identification Number (GSTIN).

GSTIN Input

GSTIN Structure:
• Digits 1-2: State Code (27)
• Digits 3-12: Permanent Account Number (PAN) (AABCU9603R)
• Digit 13: Entity registration number (1)
• Digit 14: Default character 'Z' (Z)
• Digit 15: Checksum digit (M)

Validation Status

GSTIN Format Checker: Validate GST Identification Number Online

Check whether any GSTIN is correctly formatted before putting it on an invoice or filing GST returns.

What Is a GSTIN?

GSTIN stands for Goods and Services Tax Identification Number. It is a unique 15-character alphanumeric code assigned to every registered GST taxpayer in India. It identifies the state, PAN of the business, entity type, and includes a checksum digit.

Every GST-registered business must display its GSTIN on all tax invoices, credit notes, and debit notes.

What Does the GSTIN Format Mean?

A GSTIN has a specific structure: the first two digits represent the state code, the next 10 characters are the PAN of the business, the 13th character is an entity number, the 14th is always Z, and the 15th is a check digit.

For example, a GSTIN starting with 27 indicates Maharashtra. A GSTIN starting with 29 indicates Karnataka.

Why Validate GSTIN Format?

A GSTIN with incorrect format is invalid. If you put a wrong GSTIN on an invoice, the recipient cannot match the invoice to their purchase in the GST portal. This blocks their input tax credit claim and can cause compliance issues for both parties.

Verifying GSTIN format before printing an invoice takes seconds but prevents costly errors.

How to Use the GSTIN Format Checker

Enter the 15-character GSTIN in the input field. The tool checks whether it follows the correct format, including state code, PAN structure, entity number, and the mandatory Z in position 14.

If the format is valid, you can proceed with confidence. If it fails, check the GSTIN again with your supplier or on the GST portal.

Format Check vs Checksum Validation

This tool checks the format and structure of the GSTIN. A separate checksum validator (also available on Tez Invoice) verifies that the final check digit is mathematically correct, providing a deeper level of validation.

Use both tools together for complete GSTIN verification before finalising invoices.

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Frequently Asked Questions

Common questions about GSTIN Format Checker: Validate GST Identification Number Online on Tez Invoice.

What is a GSTIN?

GSTIN is the 15-character Goods and Services Tax Identification Number assigned to every registered GST taxpayer in India.

How many characters is a GSTIN?

A GSTIN is exactly 15 characters long: a mix of digits and uppercase letters.

What does the GSTIN format look like?

State code (2 digits) plus PAN (10 characters) plus entity number (1 character) plus Z plus check digit.

Is this GSTIN format checker free?

Yes. Free with no sign up.

What happens if I put a wrong GSTIN on an invoice?

The recipient cannot match the invoice on the GST portal and their input tax credit claim may be blocked.

How is a format check different from a checksum validation?

Format check verifies the structure. Checksum validation verifies the mathematical correctness of the last digit. Use both for full validation.

Does this work on mobile?

Yes. Fully responsive.

Is my data stored?

No. Validation happens in your browser only.

Where can I find my GSTIN?

Your GSTIN is on your GST registration certificate issued by the GST portal.

Can I create a GST invoice with GSTIN on Tez Invoice?

Yes. The free Invoice Generator on Tez Invoice has a GSTIN field for your business.