GSTR-1 vs GSTR-3B: What's the Difference?

The Two Most Important GST Returns

Every GST-registered business in India must file two monthly returns: GSTR-1 and GSTR-3B. Despite their frequency, many business owners don't understand what each does or why both are required. Confusing them — or filing one without the other — leads to GST notices, blocked ITC for your customers, and interest charges.

GSTR-1: The Outward Supply Statement

GSTR-1 is a detailed, invoice-level statement of all outward supplies (sales invoices, debit notes, credit notes) made during the tax period.

What it contains: B2B invoices (each separately with HSN/SAC, tax rate, and buyer's GSTIN), B2C invoices, export invoices, nil-rated supplies, and amendments to prior periods. When to file: Monthly filers — 11th of the following month. Quarterly (QRMP) filers — 13th of the month following the quarter. Why it matters: When you file GSTR-1, your invoices appear in your buyer's GSTR-2B. If you don't file, your buyers cannot claim ITC on purchases from you. This is why businesses frequently receive calls demanding GSTR-1 filing.

GSTR-3B: The Summary Return and Tax Payment

GSTR-3B is a monthly self-declaration of total outward supplies, eligible ITC, and net tax payable. Unlike GSTR-1, it's a summary form — totals, not individual invoices.

What it contains: Total outward taxable supplies, ITC claimed by category, net tax payable, and actual tax payment (IGST + CGST + SGST + cess). When to file: Monthly filers — 20th of the following month. QRMP quarterly filers — 22nd or 24th of month following the quarter (depending on state category). Why it matters: Tax is actually paid through GSTR-3B. No payment means 18% per annum interest from the due date. The government uses GSTR-3B to calculate revenue.

Key Differences at a Glance

The Filing Sequence Every Month

GSTR-1 (by 11th) — declare all sales invoices

Review GSTR-2B (after 14th) — check ITC available from suppliers

GSTR-3B (by 20th) — pay tax based on GSTR-1 outflows minus GSTR-2B ITC

Never file GSTR-3B without checking GSTR-2B first.

Common Mistakes and Consequences

1. Filing GSTR-3B without GSTR-1: Tax is paid but buyers' ITC gets blocked — they'll call you. 2. Mismatch between GSTR-1 and GSTR-3B: If outward supplies differ, an ASMT-10 discrepancy notice follows automatically. 3. Claiming more ITC than GSTR-2B shows: Flagged automatically, results in demand notices. 4. Not filing nil returns: Even zero-transaction months require both returns. Late fee: ₹50/day per return.

QRMP Scheme

Businesses with turnover up to ₹5 crore can opt for Quarterly Return Monthly Payment. Under QRMP, both GSTR-1 and GSTR-3B are filed quarterly. Tax is paid monthly via PMT-06 challan in the first two months. The tradeoff: buyer ITC appears in GSTR-2B quarterly, which can affect monthly-filing buyers.

Conclusion

GSTR-1 and GSTR-3B serve distinct functions — one populates the ITC ecosystem, the other settles tax liability. Filing both correctly and on time is the foundation of GST compliance. Our GST team can set up a structured monthly compliance calendar for your business.