Why does a buyer's GSTIN matter?
A business registered under GST can claim back the GST it pays on purchases as input tax credit, but only if your invoice carries its GSTIN (its 15-character GST number) and your GSTR-1 reports the sale against it. The credit then shows in the buyer's GSTR-2B.
Without the GSTIN, the sale is a consumer (B2C) sale: it is totalled into Table 7 of your GSTR-1, and the buyer gets nothing back. For a business buying ₹50,000 of stock at 18%, that is ₹9,000 of credit lost, and a customer who may not order again.
Does Shopify have a GSTIN field at checkout?
No. Shopify's checkout collects names and addresses, and an optional company name, but no GSTIN. Its India help page covers tax rates and HSN codes, not the buyer's GSTIN.
How to add one
A field on the cart page (any plan)
The simplest route: a field on the cart page, labelled something like "GSTIN (for business purchases)", saved as a cart attribute. Shopify copies cart attributes onto the order as note attributes, where an invoice app can read them. It should:
- accept 15 characters and convert them to capitals;
- check the format and the check character before saving, so a typo is caught while the buyer can still fix it;
- stay optional, so consumers are not slowed down.
Shopify B2B (Shopify Plus)
Stores on Shopify Plus can sell to company accounts, which carry the company's tax registration. An invoice app can read it from there.
Orders you create yourself
For a draft order, add the GSTIN as an additional detail (a note attribute) before you send the invoice.
How do I check a GSTIN?
A GSTIN has a fixed shape:
| Characters | What they are | Example |
|---|---|---|
| 1 to 2 | State code | 29 for Karnataka |
| 3 to 12 | The business's PAN | AAAAA1234A |
| 13 | Registration number for that PAN in the state | 1 |
| 14 | Z by default | Z |
| 15 | Check character, worked out from the first 14 | 5 |
The check character catches most typos. To confirm the business is real and active, look it up on the GST portal's Search Taxpayer page, which shows the legal name, the state and whether the registration is active or cancelled. Print the legal name from the portal on the invoice, not whatever was typed.
What changes once the GSTIN is on the order?
- The invoice shows the buyer's GSTIN and legal name with yours. That is what lets them claim.
- GSTR-1 reports the sale in Table 4 (B2B), invoice by invoice, against their GSTIN, instead of netting it into Table 7.
- Credit notes on that invoice go in Table 9B (CDNR), and since 1 October 2025 the buyer must reverse its credit before your tax goes down.
- The HSN summary counts the sale in its B2B tab.
What if the buyer sends the GSTIN after paying?
A tax invoice is final once issued, so the GSTIN cannot simply be typed onto it afterwards. Collect it before payment, at the cart. If a buyer sends it later, talk to your accountant before that month's GSTR-1 is filed.
Common mistakes
- A GSTIN in the order note or the company line. Free text is easy to miss and impossible to check. Use a dedicated field.
- Accepting a GSTIN without a check. One wrong character puts the credit on someone else's return, or on no one's.
- Taking the place of supply from the GSTIN. The place of supply for goods follows where they are delivered, by the rules in section 10 of the IGST Act, not the state in the GSTIN alone.