Also known as: Goods and Services Tax Identification Number · GST number
15-character alphanumeric identification number assigned to every GST-registered business in India, encoding state, PAN, and registration entity.
GSTIN (Goods and Services Tax Identification Number) is the 15-character alphanumeric ID assigned by GSTN to every business or person registered under the GST regime. The format is precise — the first two digits are the state code (07 = Delhi, 27 = Maharashtra, 29 = Karnataka, 33 = Tamil Nadu, and so on), the next ten characters are the entity's PAN, the 13th character is the entity code (1 for the first registration in a state, 2 for the second, and so on for additional places of business), the 14th is a fixed "Z", and the 15th is a check-sum digit.
GSTIN is required on every invoice you raise (your own GSTIN) and to claim ITC on every invoice you receive (your supplier's GSTIN). A wrong or expired GSTIN on a purchase invoice means you cannot claim the ITC — and depending on the buyer's registration status, it can also mean the invoice is treated as B2C in your GSTR-1 with downstream complications.
ReadyBooks.ai performs local GSTIN format, check-sum, and state-consistency validation where the field is captured. Where the plan and configured provider allow it, an eligible user can explicitly request live verification. That response is point-in-time and provider-dependent; imported records are not automatically live-verified, and the GST portal remains authoritative for current registration status.