A GSTIN (Goods and Services Tax Identification Number) is the 15-character registration number every GST-registered business in India holds, one per state. The first two digits are the state code, the next ten are your PAN, followed by entity and check characters. As of Aug 2026, registration is mandatory once turnover crosses ₹40 lakh for goods or ₹20 lakh for services in most states.
Your GSTIN appears on every tax invoice, return, e-way bill and e-invoice you issue, and it is how the portal ties your GSTR-1 filings to your buyers' input tax credit. One PAN can hold multiple GSTINs — one per state you operate from, or separate registrations for distinct business verticals in the same state. Anyone can verify a GSTIN free on the GST portal, which is worth doing for every new supplier before you pay them.
To get one, you apply online in form REG-01 with PAN, Aadhaar authentication, proof of place of business and bank details. Approval is usually quick if Aadhaar authentication goes through cleanly. Once registered, display the GSTIN on your signboard and print it on every invoice. If you sell B2B, capture your buyer's GSTIN correctly at billing — that single field decides whether their credit lands.
The common mistake is a typo in the buyer's GSTIN in GSTR-1: the credit flows to a stranger's account and your actual customer chases you for an amendment. Also watch for suspension — mismatches or prolonged non-filing can trigger a REG-31 suspension notice, which freezes your ability to file and generate e-way bills until resolved.
Reviewed to the law in force in FY 2026-27. General information, not advice — confirm the position for your facts before acting.