GST compliance in India revolves primarily around two monthly returns: GSTR-1 and GSTR-3B. While both are filed monthly (or quarterly for the QRMP scheme), they serve very different purposes. GSTR-1 is a detailed outward supply statement — you're reporting every B2B invoice you've raised. GSTR-3B is a summary return where you report your net tax liability and pay it. Getting these right is critical: errors in GSTR-1 affect your buyers' ability to claim ITC, and errors in GSTR-3B attract interest and penalties.
GSTR-1: Your Outward Supply Statement
GSTR-1 is a detailed statement of all outward supplies (sales) made during the month. It includes every B2B invoice, B2C invoice above ₹2.5 lakh, credit notes, debit notes, export invoices, and nil-rated or exempt supplies. Buyers can see your GSTR-1 data in their GSTR-2B (auto-generated ITC statement) — so accuracy is essential for your customers.
- Filing deadline: 11th of the following month (e.g., January GSTR-1 is due by February 11)
- Quarterly filers (QRMP scheme — turnover below ₹5 crore): due by 13th of the month after each quarter
- B2B invoices: report every invoice individually with GSTIN of buyer, invoice number, date, taxable value, and GST amount
- B2C large invoices (above ₹2.5 lakh): report individually; below this threshold can be reported in aggregate
- Exports: report export invoices with shipping bill details; claim refund of IGST paid or export under LUT
- Amendments: mistakes in previous GSTR-1 can be corrected in the current month's GSTR-1 via amendment tables
- NIL GSTR-1: must be filed even if there were no outward supplies during the month
Your buyers' ITC claims depend on invoices appearing in your GSTR-1. Late or incorrect GSTR-1 filing can block your clients from claiming input tax credit, damaging your business relationships.
GSTR-3B: The Monthly Summary Return
GSTR-3B is a self-assessed summary return where you report your tax liability across all supply types and claim your input tax credit for the month. Unlike GSTR-1, GSTR-3B doesn't require invoice-level details — it's a consolidated statement. However, the tax you pay via GSTR-3B must match your GSTR-1 and GSTR-2B data over time.
- Filing deadline: 20th of the following month for taxpayers with monthly filing obligation
- QRMP quarterly filers: 22nd or 24th of the month after the quarter (depending on state)
- Box 3.1: report outward supplies (taxable, zero-rated, nil-rated, exempt, reverse charge received)
- Box 4: report eligible ITC claimed for the month (from GSTR-2B auto-populated data)
- Box 5: payment of tax — IGST, CGST, SGST, cess; paid from electronic cash or credit ledger
- Tax must be paid by the due date — late payment attracts 18% annual interest on the outstanding amount
- Nil GSTR-3B: file even if no transactions occurred; easier filing via SMS for nil filers
Input Tax Credit (ITC) Claims and GSTR-2B
Input Tax Credit allows you to offset the GST you paid on purchases against the GST collected on your sales. From FY 2021-22, ITC is governed by GSTR-2B — a system-generated, auto-populated statement that shows ITC available based on your suppliers' GSTR-1 filings. You can only claim ITC that appears in your GSTR-2B.
- ITC available only if the supplier has filed GSTR-1 and the invoice appears in your GSTR-2B
- ITC must be claimed within the earlier of: November 30 of the next financial year or the date of filing the annual return (GSTR-9)
- Blocked ITC: GST on motor vehicles (except for transportation business), food and beverages, club membership, beauty treatment, and goods for personal consumption
- Reverse charge mechanism (RCM): you pay GST as a recipient (not the supplier) on specified goods and services — e.g., legal services from unregistered advocates, import of services
- ITC on RCM payments is available only in the month of actual payment — not on accrual basis
- Reconcile GSTR-2B with your books monthly to catch missing invoices or supplier non-compliance early
If a supplier has not filed their GSTR-1, their invoices will not appear in your GSTR-2B and you cannot claim ITC. Always check GSTR-2B before finalising GSTR-3B.
Late Fees, Interest, and Penalties
Late filing of GST returns in India attracts both a fixed late fee and, for tax payments, interest. The late fee structure was revised to make it less punitive for nil filers, but it still adds up quickly if you miss multiple months.
- Late fee for GSTR-1: ₹50/day (₹25 CGST + ₹25 SGST) for returns with tax liability; ₹20/day for nil returns
- Late fee for GSTR-3B: ₹50/day with tax liability; ₹20/day for nil filers; maximum ₹10,000 per return
- Interest on late tax payment: 18% per annum on the net tax liability (from due date to actual payment date)
- GSTR-3B filing is required to unlock subsequent months' GSTR-1 filing — non-filing blocks your entire compliance chain
- GSTIN cancellation: IRAS can cancel your GSTIN for consecutive non-filing (3 or more months)
- Fraudulent ITC claims: 100% penalty on the fraudulently claimed amount plus possible arrest under GST Act
Set calendar reminders for the 10th and 20th of every month — your GSTR-1 and GSTR-3B deadlines. Missing even one month creates a cascading compliance problem.
Annual Return (GSTR-9) and What Bookub Automates
In addition to monthly returns, GST-registered businesses must file an Annual Return (GSTR-9) by December 31 of the following financial year. It reconciles your monthly filings and provides a consolidated view of your annual tax position. For businesses with turnover above ₹2 crore, a GST Audit (GSTR-9C) is also required.
- GSTR-9 due date: December 31 of the following financial year (e.g., FY 2024-25 annual return due December 31, 2025)
- GSTR-9 is optional for taxpayers with annual turnover below ₹2 crore
- GSTR-9C (reconciliation statement): mandatory for turnover above ₹5 crore; requires CA certification
- ITC mismatch between GSTR-3B and GSTR-9 must be explained or reversed
- What Bookub handles: automated GSTR-1 preparation from invoices, GSTR-3B summary generation, ITC reconciliation with GSTR-2B, one-click filing to GST portal
- Bookub also tracks upcoming deadlines and sends alerts before due dates
The GSTN portal offers a free GSTR-1 and GSTR-3B filing facility, but the manual data entry and reconciliation process is time-consuming. Accounting software like Bookub reduces filing time from hours to minutes.
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GSTR-1 prepared from invoices, GSTR-3B auto-computed, ITC reconciled, and filed directly to the GST portal.
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