Invalid GSTIN

A GSTIN in your upload failed validation — either it is malformed, or it is not the GSTIN the portal expected for this account.

What it means

The portal checks every GSTIN in the file against the 15-character structure and its checksum, and it checks that the supplier GSTIN in the JSON matches the account you are uploading to. A single transposed character is enough to fail, because the final checksum digit is derived from the preceding fourteen. This is the most frequent GSTR-1 upload failure, and it is almost always a data-entry problem rather than a portal problem.

Common causes

• A recipient GSTIN was typed or imported with a transposed or missing character.
• The JSON was generated under one GSTIN and uploaded to a different account — common in practices handling multiple clients.
• A GSTIN carries stray spaces, lowercase letters, or a leading apostrophe left behind by Excel.
• A B2B invoice was recorded against a customer who is actually unregistered, so no valid GSTIN exists.

How to fix it

1. Open the error report the portal generates and note which invoices are flagged — it names them.
2. Check the flagged GSTINs are exactly 15 characters: 2-digit state code, 10-character PAN, 1 entity digit, the letter Z, then the checksum character.
3. Confirm you are uploading to the correct client account. Practices juggling several GSTINs hit this constantly.
4. Strip whitespace and force uppercase — Excel exports frequently carry both problems invisibly.
5. If the customer is genuinely unregistered, move the invoice out of the B2B section into B2C.