When is GST registration mandatory for a startup in India?

You must register for GST if any of these apply:

• Goods: aggregate turnover exceeds ₹40 lakh (₹20 lakh in some special-category states)
• Services: aggregate turnover exceeds ₹20 lakh (₹10 lakh in some special-category states)
• You make inter-state taxable supplies (with limited exceptions)
• You sell through an e-commerce operator that is required to collect TCS
• You are liable under reverse charge or other notified cases

Turnover is counted across India, not per GSTIN. Many early SaaS and agency founders register earlier than the threshold so they can issue tax invoices to GST-registered customers who want input credit.

Registration is on the GST portal. After that you file returns on the prescribed cycle (typically GSTR-1 and GSTR-3B). Missing filings attract late fees quickly — treat compliance as a monthly habit, not a year-end task.