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 Checksum Validator: Verify the Check Digit of Any GSTIN

Mathematically verify whether a GSTIN's check digit is correct with this free online GSTIN checksum validator.

What Is a GSTIN Checksum?

The last character of a GSTIN is a check digit computed mathematically from the other 14 characters. It acts as a built-in error-detection mechanism. If any character in the GSTIN is wrong, the check digit will not match.

By validating the checksum, you can be confident that the GSTIN has not been mistyped or randomly generated.

Format Check vs Checksum Validation

A format check verifies that the GSTIN has the right structure: 15 characters, correct state code format, correct PAN structure, and Z in position 14. A checksum validation goes one step further and mathematically verifies that the final digit is correct.

A GSTIN can pass the format check but still have an incorrect check digit. Both validations together give you the highest confidence in a GSTIN's validity.

Why Validate the GSTIN Checksum?

Incorrect GSTINs cause invoice mismatches on the GST portal. This prevents your customers from matching your invoice to their purchases, blocking their input tax credit claims.

Verifying the checksum before putting a GSTIN on an invoice or in a system adds a critical layer of verification and demonstrates professional business practices.

How to Use the Checksum Validator

Enter the 15-character GSTIN in the input field. The tool applies the checksum algorithm and tells you whether the check digit is correct.

If the validation fails, the GSTIN has been mistyped. Ask your client or supplier to confirm their GSTIN and re-enter it.

Where to Verify GSTIN Officially

For official verification including whether a GSTIN is currently active, visit the GST portal at www.gst.gov.in. This Tez Invoice tool validates format and checksum locally in your browser for quick checks without needing to access external services.

Always do an official portal check for high-value transactions where you need to confirm GSTIN is active.

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Frequently Asked Questions

Common questions about GSTIN Checksum Validator: Verify the Check Digit of Any GSTIN on Tez Invoice.

What is a GSTIN checksum validator?

It mathematically verifies the last character (check digit) of a GSTIN to confirm it was computed correctly from the first 14 characters.

Why is the check digit important?

The check digit acts as an error detector. If any character in the GSTIN is wrong, the check digit will not validate, revealing the error.

Is this validator free?

Yes. Free with no sign up.

What is the difference between format check and checksum check?

Format check verifies structure. Checksum check verifies the mathematical accuracy of the last digit. Both are needed for thorough validation.

What if the checksum validation fails?

The GSTIN was mistyped or is invalid. Ask the party who gave it to you to confirm the correct GSTIN.

Does this replace official GST portal verification?

No. This is for quick local checks. For official status verification, use the GST portal.

Does this work on mobile?

Yes. Fully responsive.

Is my data stored?

No. Validation happens in your browser only.

How many characters is a valid GSTIN?

Exactly 15 characters.

Can I add GSTIN to invoices on Tez Invoice?

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