GSTR-1 vs GSTR-3B: What Each Return Captures, When to File, and How They Connect

TL;DR

Every regular GST taxpayer files GSTR-1 and GSTR-3B each month. They look similar but answer different questions: GSTR-1 is the outward-supply register — every B2B invoice with GSTIN, every B2C invoice by state and rate, every credit note, every debit note, every advance receipt. GSTR-3B is the summary self-assessment — output tax computed, input tax credit (ITC) claimed, ineligible ITC reversed, net balance tax paid to the government. GSTR-1 is filed first (by the 11th) so suppliers’ invoices appear in their customers’ GSTR-2B by the time GSTR-3B is filed (by the 20th).

What GSTR-1 Captures

GSTR-1 is a four-purpose statement of every invoice your business issued during the month:

Table 4 — B2B invoices. Every taxable invoice issued to a registered buyer. Each row carries the buyer’s GSTIN, invoice number, taxable value, IGST or CGST + SGST split, HSN code, and the invoice date. The buyer’s GSTR-2B automatically picks this up for their ITC claim, so an error here directly costs your customer money — disputes over missing invoices are the most common reason vendors get payment withheld.

Table 5 — B2C invoices. State-wise aggregate of taxable value plus integrated tax or central + state tax, broken down by GST rate (5%, 18%, 28%, etc.). B2C invoices are aggregated, not line-itemised — so a Mumbai restaurant with 200 retail bills files one row per rate per state instead of 200 rows.

Table 6 — Exports and deemed exports. Invoices with shipping bill numbers, deemed export declarations, and supplies to SEZs. Letter of Undertaking (LUT) details are captured here for zero-rated export supplies.

Table 7 — Tax liability (advance receipts and reverse charge). Advances received against future supply (taxable at receipt under Section 12 for goods, Section 13 for services) and supplies attracting reverse charge where the recipient pays GST.

Table 8 and 9 — Advances, credit notes, debit notes. Adjustments for advances (now rare after the 2019 amendment for services), credit notes issued against original invoices, debit notes for additional charges, and refund vouchers.

Table 12 — HSN-wise summary. Aggregate of all supplies by HSN code at the digit length required for the taxpayer’s turnover band.

Due date: 11th of the following month (13th for QRMP filers under the QRMP scheme). January 2020 onwards, this due date is fixed by Section 37 read with the 22nd GST Council meeting — no quarterly or annual relaxation for regular filers.

What GSTR-3B Captures

GSTR-3B is the only return that actually triggers tax payment. It is a six-table summary covering:

Table 3.1 — Outward and reverse-charge supplies. Aggregate taxable value plus IGST, CGST, SGST on supplies made by the taxpayer and on supplies received under reverse charge. The numbers here should reconcile with GSTR-1 + reverse-charge liability for the period.

Table 4 — Eligible ITC. Auto-populated from GSTR-2B (the static statement generated at month-end from your suppliers’ GSTR-1 filings). You can edit values in some cases (reversal entries, additional ITC not yet reflected), but the audit trail is preserved.

Table 5 — ITC reversed. Reversal under Rule 42 (input services used partly for exempt supplies), Rule 43 (capital goods used for exempt supplies), non-payment to suppliers within 180 days (Section 16(2)(b)), and other reversals.

Table 6 — Ineligible ITC. Blocked credits under Section 17(5): motor vehicles (with exceptions for specific industries), food and beverages, club membership, health and life insurance (with exceptions), rent-a-cab, health services, beauty treatment, cosmetics. These amounts appear in GSTR-2B but the taxpayer must reverse them in Table 6.

Table 7 — Interest and late fees. Section 50 interest on delayed tax payment (18% per annum, 1.5% per month). Section 47 late fees for delayed return filing (₹50/day, ₹20/day for NIL returns, capped per Act).

Table 8 — Tax paid. Net of all the above tables, broken down by IGST / CGST / SGST / Cess. Payment is via Electronic Cash Ledger or Electronic Credit Ledger (ITC).

Due date: 20th of the following month (22nd-24th for QRMP filers, depending on State). Form GSTR-3B has a single due date — there is no staggered timeline like GSTR-1.

How They Connect in the Monthly Cycle

Day 1 to 11: Prepare and file GSTR-1. The portal allows two modes: direct entry on the online form (only practical for very low invoice counts) or bulk upload via offline Excel/JSON template (the standard mode for businesses with more than a few hundred invoices per month). Validation runs check GSTIN format, HSN code validity, tax-rate-versus-HSN pairing, and inter-State vs intra-State classification. Once filed, an Acknowledgement Reference Number (ARN) is generated.

Day 12 to 13: Auto-reconciliation. The GSTN system propagates your GSTR-1 data into every supplier’s GSTR-2A and GSTR-2B. By day 13, your GSTR-2B is locked for the previous month.

Day 14 to 20: Prepare and file GSTR-3B. Open GSTR-3B, pull in the auto-populated ITC from GSTR-2B, add your reversals and ineligible credits, compute net tax payable, generate the Electronic Cash Ledger debit, and submit. The system blocks filing until the cash ledger has sufficient balance, so most taxpayers top up their bank-ICICI / HDFC-ledger via NEFT/RTGS 2-3 days before the due date.

The two returns are not redundant. A common mistake by new taxpayers is to file only GSTR-3B (the only one that triggers payment) and skip GSTR-1 — but GSTR-3B without GSTR-1 means your customers cannot claim ITC on what they bought from you, which leads to withheld payments and supplier disputes, even if you have paid the GST.

Annual Return GSTR-9

GSTR-9 is the annual reconciliation return, due 31 December of the following financial year (so GSTR-9 for FY 2025-26 is due 31 December 2026). It is a single-document reconciliation between the cumulative GSTR-1 and GSTR-3B filed during the year and the audited annual accounts. Differences above ₹1 lakh per head attract notice and may require a revised GSTR-9 or GSTR-9C (reconciliation statement for turnover above ₹5 crore).

Common Errors That Trigger Notices

Based on FinTax24’s review of 6,000+ monthly return filings, the top five errors are:

1. HSN code mismatch. Using 4-digit HSN when 6-digit is required (or vice versa) for the taxpayer’s turnover band. The threshold dropped to ₹5 crore aggregate turnover in 2021 — the 6-digit HSN requirement now applies broadly.
2. Tax rate-versus-HSN mismatch. Charging 18% on a HSN code that is in the 12% slab (or 12% on one in the 18% slab, though the 12% slab was discontinued in the 2025-26 rationalisation). The most common cause of GST department ASMT-10 notices.
3. Inter-State vs intra-State confusion. Treating a supply as intra-State when the buyer is in a different state, or vice versa. Causes IGST vs CGST + SGST mismatches that may require retrospective amendment.
4. ITC claimed on blocked items. Section 17(5) blocks ITC on motor vehicles, food and beverages, club memberships, and cosmetics unless specific exceptions apply (e.g., used for further supply, or specific industries like training or transportation).
5. Advance receipt treatment. Declaring advances against future supply under the wrong time-of-supply provision (Section 12 for goods, Section 13 for services). Most common in subscription-based businesses and event management.

How FinTax24 Files Both Returns

Our process for a typical monthly filing cycle:

Day 1-3: Data extraction. We pull from Tally, Zoho Books, QuickBooks, or Busy via API or scheduled export. Manual entries are collated and double-checked against bank statement inflows.

Day 4-7: GSTR-2B reconciliation. We compare your purchase register with the GSTR-2B auto-generated on day 13, identify missing supplier invoices, and email non-compliant suppliers to file their GSTR-1. Late-filed supplier GSTR-1 = your lost ITC; this step recovers 5-15% of total ITC in our experience.

Day 8-10: GSTR-1 preparation. HSN code validation, tax rate check, inter/intra-State classification, credit-note timing. Filing on day 11.

Day 12-18: GSTR-3B preparation. Open GSTR-2B on day 13, apply reversals and ineligible credits, compute net tax. Generate the PMT-06 challan.

Day 19-20: GSTR-3B filing. Top up cash ledger the day before. Submit. ARN recorded.

We file 12,000+ returns per year with a 100% zero-penalty record. The same discipline applies whether your turnover is ₹20 lakh or ₹200 crore.

When to Use an Expert

Self-filing works for the first year when turnover is small and there are 50-100 invoices. Once you cross ₹50 lakh turnover, hire a professional — the cost (₹8,000-25,000 a year) is a fraction of the late fee (₹50/day, capped at ₹10,000 per return period per Act) and the avoided interest at 18%. FinTax24’s GST Return Filing service handles both returns monthly with reconciliation, supplier follow-up, and an annual GSTR-9 included.