GST Compliance for Indian Startups: Registration, Returns & the Deadlines That Matter

GST compliance for an Indian startup comes down to three things: registering when you cross the threshold (₹40 lakh for goods, ₹20 lakh for services — or immediately for inter-state or e-commerce supply), filing your returns on time (GSTR-1 and GSTR-3B monthly or quarterly, plus the annual GSTR-9), and reconciling your input tax credit. Miss a return and you owe a per-day late fee plus 18% interest on any tax paid late. This guide maps the whole GST obligation set for a startup, with the deadlines and the traps.

When you must register for GST

You must register once you cross the turnover threshold — ₹40 lakh for goods, ₹20 lakh for services in most states (lower in special-category states). But several triggers require registration regardless of turnover:

• Inter-state supply of goods or services
• E-commerce sales (selling through a marketplace)
• Being liable under reverse charge (RCM)
• Exporters (needed to claim refunds / file an LUT)

Many startups need GST registration earlier than they expect because of inter-state supply — a common surprise for a SaaS company with customers in another state.

The returns you file

Monthly / quarterly

• GSTR-1 — your outward supplies (sales). Monthly filers by the 11th; QRMP filers quarterly.
• GSTR-3B — the summary return where you declare output tax, claim input credit, and pay the net. Monthly filers by the 20th; QRMP quarterly with monthly payment.

Annual

• GSTR-9 — the annual return, above the prescribed turnover.
• GSTR-9C — the reconciliation statement, above ₹5 crore.

Situational

• E-invoicing once your turnover crosses ₹5 crore.
• RFD-01 to claim export/inverted-duty refunds.

The deadlines and what missing them costs

Late filing triggers two separate charges: a late fee (₹50/day, ₹20 for nil returns) and 18% p.a. interest on tax paid late — explained in full in GST late fees and interest. Beyond the money, a filing gap shows up in diligence and can block your input credit chain for customers.

The traps startups hit

• Input Tax Credit surprises — you can only claim ITC that appears in your auto-drafted statement, and some credits are blocked. See Input Tax Credit eligibility.
• The nil-return skip — "nothing to report" still needs a filed nil return, or the late fee runs anyway.
• Reverse charge — you can owe GST on purchases (e.g. from unregistered suppliers or certain services) even though you're the buyer.
• Export zero-rating — SaaS/service exporters must file an LUT to supply without charging GST.

Track every GST return with proof

GST is a monthly rhythm with annual and situational overlays — exactly what slips in a busy month. ComplianceStack builds your applicable GST calendar (registration status, GSTR-1/3B, annual returns, e-invoicing, RCM) with reminders and the filed acknowledgement stored as evidence. Get your free compliance health check — or run the numbers on the GST late-fee calculator.