How to File Monthly GST Returns in India — GSTR-1 and GSTR-3B
GST-registered businesses with turnover above ₹5 crore (or those not on the QRMP scheme) must file two returns every month: GSTR-1 (details of outward supplies by the 11th) and GSTR-3B (summary return with net tax payment by the 20th). Missed filings block e-way bill generation and attract late fees.
Before you start
- GSTIN and GST portal credentials
- Sales invoices for the month (B2B, B2C, exports, credit/debit notes)
- Purchase invoices and input tax credit (ITC) eligibility assessment
- Bank account details for tax payment via challan
- Previous month's ITC balance in Electronic Credit Ledger
Step-by-step
Compile and Classify Sales Invoices
Segregate your sales invoices into: B2B (registered buyers — need their GSTIN), B2C large (interstate sales > ₹2.5 lakh to unregistered buyers), B2CS (consolidated for other B2C), exports (with/without payment of tax), and nil-rated/exempt supplies. Errors here cause reconciliation mismatches with your buyers' GSTR-2B.
File GSTR-1 by the 11th
Log in to gst.gov.in and navigate to GSTR-1 for the relevant tax period. Enter or upload invoice data using the offline tool (Excel-based) or API integration. Submit and file the return. Once filed, GSTR-1 data flows to your buyers' GSTR-2B the same night.
Reconcile ITC from GSTR-2B
Download your auto-generated GSTR-2B on or after the 14th. Compare it with your purchase register — claim ITC only for invoices appearing in GSTR-2B. ITC on missing invoices must wait for the supplier to file or must be reversed if unclaimed after the deadline.
Compute Net Tax Liability for GSTR-3B
Calculate Output Tax (from your GSTR-1 data), deduct eligible Input Tax Credit (from GSTR-2B), and determine the net tax payable in cash. Prepare separate computations for IGST, CGST, and SGST.
Create Payment Challan and Pay Tax
On the GST portal, create a payment challan (Form PMT-06) for the net cash tax liability and pay via net banking or NEFT/RTGS. The payment credits your Electronic Cash Ledger, from which the liability is offset.
File GSTR-3B by the 20th
Navigate to GSTR-3B for the month. Enter consolidated outward supply details, ITC claims, and reverse charge liabilities. Offset the tax liability using the Electronic Cash and Credit Ledger balances. Submit and file. Download the filed return acknowledgment for records.
Common mistakes to avoid
- Filing GSTR-1 after the 11th — late GSTR-1 blocks your buyers from claiming ITC and attracts a late fee of ₹50/day (₹20/day for nil returns), capped at ₹10,000.
- Claiming ITC for invoices not in GSTR-2B — such claims are invalid and will be reversed in assessment with interest at 18% per annum.
- Not reversing ITC on non-business or personal expenses — ITC is only available for goods and services used in the course or furtherance of business.
- Ignoring the GSTR-1 vs GSTR-3B reconciliation — if output tax in 3B is lower than in GSTR-1, the excess is treated as an understatement and attracts interest and penalty.
Frequently asked questions
What is the QRMP scheme and who is eligible?
The Quarterly Return Monthly Payment (QRMP) scheme allows taxpayers with annual aggregate turnover up to ₹5 crore to file GSTR-1 and GSTR-3B quarterly while making monthly tax payments through a fixed-sum challan. It reduces compliance burden for small businesses.
Can I amend a filed GSTR-1?
Yes. Amendments to B2B invoices reported in a prior GSTR-1 can be made in the 'Amendments to B2B' section of the next month's GSTR-1. There is no separate amendment return for GSTR-1.
What happens if I miss the GSTR-3B deadline?
A late fee of ₹50 per day (₹20/day for nil returns) applies, subject to a maximum of ₹10,000 per return. Additionally, interest at 18% per annum is charged on any outstanding tax from the due date.
Is GSTR-1 filing mandatory even if I have no sales in a month?
Yes. A nil GSTR-1 must be filed for months with zero outward supplies. You can file a nil GSTR-1 via SMS (sending NIL
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