GSTIN
Also called: GST number, GST identification number
What is GSTIN?
GSTIN is the 15-character Goods and Services Tax Identification Number issued to every registered business. It encodes the state code, the business PAN, an entity number for that PAN within the state, and a check digit, which is why a valid GSTIN can be sanity-checked before you save it.
Why GSTIN matters
Your GSTIN must appear on every tax invoice you issue, and your customer's GSTIN must appear on B2B bills for them to claim input tax credit. A missing or mistyped GSTIN is the most common reason a customer's credit claim fails and the invoice comes back to you.
How GSTIN works in practice
Store your GSTIN once in your billing profile so it prints on every document, and capture the customer's GSTIN at the point of billing for business customers. Check the first two digits against the customer's state, because that pair decides whether you charge CGST plus SGST or IGST.
Worked example
In 27AAAAA0000A1Z5, the leading 27 is the state code for Maharashtra and the ten characters after it are the business PAN.
Frequently asked questions
Yes. GSTIN is the formal name for what most people simply call their GST number.