Glossary: Tax
GST number
A GST number is the registration number a tax authority gives a business registered for goods and services tax. In India it is the 15-character GSTIN. Australia and Canada also have a GST, but use a different number (the ABN, and the GST/HST account number).
In detail
The India GSTIN has 15 characters. The first two digits are the state code, the next ten are the business's PAN, then come an entity number, the letter Z and a check character. A format like 22AAAAA0000A1Z5 is a commonly used sample pattern, not a real number.
Sellers ask Indian business buyers for the GSTIN for three reasons. A B2B invoice that carries the buyer's GSTIN lets the buyer claim input tax credit. The seller needs it to know whether to issue a B2B invoice rather than a consumer one. And the buyer's state, set by the first two digits, helps decide whether the sale is charged as CGST and SGST within a state or as IGST between states. Confirm the rules with an accountant.
Validate the number before you accept it. A format check catches typing errors, but it does not show whether the registration is active or has been cancelled. Look the number up on the government GST portal, or use a lookup service, and keep the status and the date you checked.
Outside India, ask for the number your buyer's country uses. Australian buyers give an ABN, and Canadian buyers give a business number with a GST/HST account. A VAT number is the EU and UK equivalent, so do not mix them up on one form.
Example
An Indian retailer enters 22AAAAA0000A1Z5 (a sample-format number, not a real one) on a wholesale application. The format passes, and the seller then checks that the registration shows as active before approving the account and issuing GST invoices to it.
In BSS B2B apps
BSS B2B Solution's registration form has an India GST field that checks the number with a lookup service as the buyer types, and accepts it only when the status is Active. It blocks submission only when the field is marked required. The GST field needs a paid plan, see the pricing page.
Related use cases
Learn more
Read the Tax and compliance hub for guides, use cases and setup docs, or the complete Shopify B2B guide.