GSTR-1 vs GSTR-3B — The 2026 Difference Guide for Indian Businesses

Every GST-registered business in India files two returns each month: GSTR-1 and GSTR-3B. They sound similar, share data, and arrive in the same dashboard — but they have completely different jobs. Miss either one, and the consequences stack up fast: late fees of ₹50 a day, 18 percent annual interest on unpaid tax, blocked input tax credit for your buyers, and DRC-01B mismatch notices from the GST Network. This 2026 guide explains both returns side by side, lays out the exact due dates, and walks through the top four mistakes that cost real money.

TL;DR — the 30-second difference

GSTR-1 is an informational return. You list every outward supply you raised during the month — invoice number, buyer GSTIN, taxable value, tax amount. The system uses this data to feed your buyers' GSTR-2B so they can claim input tax credit. No money changes hands when you file GSTR-1.

GSTR-3B is the cash-out return. You declare summary totals of your outward supplies, your eligible ITC, and the net GST payable — then you pay it. No GSTR-3B, no tax payment, no compliance.

What is GSTR-1?

GSTR-1 is the monthly (or quarterly) statement of all outward supplies — every sale, every credit note, every debit note you issued during the period. It's invoice-level for B2B transactions and summary-level for B2C, with HSN-wise totals at the bottom.

The return has 13 tables. The big ones are Table 4 (B2B invoices), Table 5 (large B2C inter-state), Table 7 (small B2C consolidated), Table 9 (amendments to previous months), Table 11 (advances received), and Table 12 (HSN-wise summary). For a typical Chennai freelancer, only Tables 4, 7, 9 and 12 ever get filled.

The due date for monthly filers is the 11th of the next month. So April 2026 supplies must be reported by 11 May 2026. Under the QRMP scheme — open to taxpayers with annual turnover up to ₹5 crore — you file the full GSTR-1 quarterly by the 13th of the month after the quarter ends. You can also push B2B invoices early via the Invoice Furnishing Facility (IFF) in months 1 and 2 of the quarter, so your buyers don't wait three months for their ITC.

Once filed, GSTR-1 cannot be revised. Errors are corrected through Table 9 in the next month's return, where you amend a previously reported invoice. The amendment can change taxable value, tax amount, place of supply — but not the original invoice number or buyer GSTIN.

What is GSTR-3B?

GSTR-3B is the summary self-declaration return where you actually pay GST. It has six sections: outward supplies (3.1), inter-state supplies to unregistered persons (3.2), eligible ITC (4), values of exempt/nil-rated/non-GST supplies (5), and payment of tax (6).

You don't list invoices in GSTR-3B. You enter consolidated totals: total taxable outward supplies, total IGST, total CGST, total SGST, total cess, and the same breakdown for ITC. The portal computes the net liability and lets you pay it via cash ledger (using PMT-06 challans) or set off against the credit ledger.

The due date for monthly filers is the 20th of the next month. Under QRMP, the quarterly GSTR-3B is due by the 22nd or 24th of the month after the quarter ends, depending on which state group you're in. The split was introduced to ease load on the GSTN servers and gives smaller-state taxpayers two extra days.

Once filed, GSTR-3B is non-revisable. There's no equivalent of GSTR-1's Table 9 amendment facility. If you over-reported tax, adjust in the next month's GSTR-3B. If you under-reported, pay the differential with 18 percent interest in the next return. If a customer cancels a sale you've already reported, issue a credit note in your GSTR-1 and reduce the outward supplies value accordingly in the next GSTR-3B.

Side-by-side comparison

How they connect — auto-population and reconciliation

The two returns aren't independent — they're stitched together by GSTR-2B, the auto-generated ITC statement. Here's the flow.

1. Suppliers file GSTR-1 by the 11th. Every B2B invoice they declare carries the buyer's GSTIN.
2. GSTN compiles GSTR-2B on the 14th. For each registered buyer, the system aggregates every invoice where their GSTIN appears, plus credit notes and import data, into a static read-only statement.
3. Buyers see GSTR-2B on the portal. This becomes the ceiling for ITC claims under Rule 36(4) and Section 16(2)(aa) — you can only claim what's in your GSTR-2B.
4. Buyers file GSTR-3B by the 20th. The portal pre-populates the eligible ITC values from GSTR-2B. You can edit downward (to exclude blocked credits, personal use, etc.) but not upward beyond what suppliers reported.

This is why filing GSTR-1 on time is a two-party concern. If you slip past the 11th, your invoice doesn't make it into your buyer's 14th-of-the-month GSTR-2B, your buyer can't claim ITC in their 20th GSTR-3B, and you get an angry call asking when you'll file. Multiply by 50 customers and one missed deadline becomes a customer service crisis.

The reconciliation rule the GSTN enforces is: GSTR-3B tax should match GSTR-1 tax within 10 percent. If your GSTR-1 reports ₹2,00,000 of outward GST and your GSTR-3B reports only ₹1,50,000 paid, the system sees a 25 percent gap and issues a DRC-01B intimation. You then have 30 days to either pay the differential with interest or file an explanation (Form DRC-01B Part B) defending the variance.

Due dates 2026

Group A states (22nd GSTR-3B due date): Andhra Pradesh, Karnataka, Kerala, Tamil Nadu, Telangana, Andaman & Nicobar, Lakshadweep, Puducherry, Chhattisgarh, Madhya Pradesh, Gujarat, Maharashtra, Goa, Daman & Diu, Dadra & Nagar Haveli.

Group B states (24th GSTR-3B due date): Himachal Pradesh, Punjab, Uttarakhand, Haryana, Rajasthan, Uttar Pradesh, Bihar, Sikkim, Arunachal Pradesh, Nagaland, Manipur, Mizoram, Tripura, Meghalaya, Assam, West Bengal, Jharkhand, Odisha, Jammu & Kashmir, Ladakh, Chandigarh, Delhi.

5 worked examples

Example 1 — Chennai freelancer, monthly filer

Bala is a designer in Chennai with monthly turnover of ₹3,00,000. For April 2026 sales, he files GSTR-1 by 11 May 2026 listing each B2B invoice. He files GSTR-3B by 20 May 2026 declaring ₹54,000 outward GST (18 percent of ₹3,00,000), claims ₹3,000 ITC on his software subscriptions, and pays the net ₹51,000 via cash ledger.

Example 2 — Mumbai SMB, QRMP filer

Anjali runs a packaging firm in Mumbai with annual turnover of ₹3 crore. She opted into QRMP. For the April-June 2026 quarter, she pays ₹2,00,000 tax via PMT-06 by 25 May (month 1) and another ₹2,00,000 by 25 June (month 2). She files quarterly GSTR-1 by 13 July and quarterly GSTR-3B by 22 July (Maharashtra is Group A). She optionally pushed her ten biggest B2B invoices via IFF on 13 May so her buyers got their ITC immediately.

Example 3 — Mismatch and DRC-01B

Bala's GSTR-1 for May 2026 reports ₹5,00,000 of outward supplies (₹90,000 tax). His GSTR-3B reports ₹4,00,000 outward supplies (₹72,000 tax) — he forgot one ₹1,00,000 invoice in the summary. The GSTN system spots the 20 percent mismatch and issues a DRC-01B notice. Bala has 30 days to pay the ₹18,000 differential plus 18 percent interest from 20 June, or to file a Part B explanation.

Example 4 — Buyer ITC blocked

Reliance Retail buys ₹10,00,000 worth of services from Bala in May 2026. Bala raises the invoice with ₹1,80,000 IGST. Bala forgets to file his May GSTR-1 by 11 June. Reliance's GSTR-2B on 14 June shows no entry for that invoice — they cannot claim the ₹1,80,000 ITC in their 20 June GSTR-3B. Reliance calls Bala, threatens to deduct the ₹1,80,000 from his next payment, and Bala files GSTR-1 immediately with a ₹50/day late fee.

Example 5 — NIL return

Bala has zero sales in April 2026 (he was on holiday). His GSTIN is still active, so he must file NIL GSTR-1 by 11 May and NIL GSTR-3B by 20 May. Both can be filed via SMS — text "NIL R1 [GSTIN] 042026" to 14409 for GSTR-1, and "NIL 3B [GSTIN] 042026" for GSTR-3B. Skipping a NIL return costs ₹20 per day even though no tax was due.

Top 4 mistakes that cost real money

Mistake 1 — Filing GSTR-3B without first filing GSTR-1

The portal allows it, which makes it tempting when you're racing the 20th deadline. But you've now reported tax in GSTR-3B that doesn't appear in any buyer's GSTR-2B. Your buyers can't claim ITC, the system flags the mismatch, and you'll spend the next month fielding emails. Always file GSTR-1 first — even if it means filing GSTR-3B a day later inside the deadline window.

Mistake 2 — Reporting outward supplies in GSTR-1 but underpaying in GSTR-3B

This is the most common DRC-01B trigger. You diligently report all 50 invoices in GSTR-1, then forget to add three of them to your GSTR-3B summary because they were entered into a different sheet. The mismatch is visible to GSTN within hours of you filing GSTR-3B. Reconcile the summary against your GSTR-1 totals before hitting submit.

Mistake 3 — Missing the 20th GSTR-3B due date

Across India, GSTR-3B is the single most-skipped return because the 20th falls in the middle of month-end pressure for many businesses. Late filing means ₹50 per day late fee plus 18 percent annual interest on the entire tax payable — even if the tax was sitting in your cash ledger ready to set off. Set a calendar reminder for the 17th and treat the 20th as immovable.

Mistake 4 — Forgetting to file NIL returns when there are no sales

An idle GSTIN still owes returns. Six consecutive missed monthly returns trigger automatic GSTIN suspension under Rule 21A. Reactivation requires filing all pending returns plus late fees. ByteZBridge sends a free reminder on the 5th and the 17th of every month so you never miss a deadline.

Frequently asked questions