GSTIN

GSTIN (Goods and Services Tax Identification Number) is the 15-character alphanumeric identifier issued to every taxpayer registered under India's Goods and Services Tax (GST) regime. Replaces the legacy TIN, Service Tax Number, and Excise Number for indirect taxes.

Structure decoded — using `29ABCDE1234F1Z5` as an example:

• Positions 1–2 — State code: `29` = Karnataka. Two-digit code as per the Indian Census 2011 (e.g., 27 = Maharashtra, 07 = Delhi, 33 = Tamil Nadu).
• Positions 3–12 — PAN: `ABCDE1234F` is the PAN of the registered taxpayer.
• Position 13 — Entity number within the state under the same PAN. Allows multiple registrations under one PAN (e.g., different business verticals or SEZ units).
• Position 14 — Default 'Z': reserved alphabet, currently fixed.
• Position 15 — Check digit: alphanumeric checksum for validation.

Who must register (Section 22, 24 of CGST Act):

• Aggregate turnover exceeding the threshold — ₹40 lakh for goods (₹20 lakh in special category states); ₹20 lakh for services (₹10 lakh in special category states).
• Mandatory irrespective of turnover (Section 24): inter-state supply, e-commerce operators, casual taxable persons, non-residents, persons required to deduct TDS under GST, input service distributors, agents, e-commerce sellers, OIDAR services from outside India.

State-wise registration:

GSTIN is state-specific. A company operating in 5 states needs 5 separate GSTINs (one per state) under the same PAN — but the company is a single legal entity. Each GSTIN files its own GSTR-1 / GSTR-3B / GSTR-9.

Why this matters for cap-table / governance:

• Many vendor / customer onboardings require GSTIN.
• GSTIN appears on every B2B tax invoice (mandatory under Rule 46 of the CGST Rules).
• Mismatch between PAN on GSTIN and PAN on bank account / TDS trips KYC checks at counterparties.
• For startups operating from a single state and below threshold, voluntary registration is common — required to claim input tax credit on purchases.

Pitfall: Adding a new state (warehouse, branch office) without timely GSTIN registration triggers heavy penalties and denial of ITC on input supplies.