GSTR-1 vs GSTR-3B: Key Differences Explained (2026)

"Why do I need to file two returns for the same month?" — This is the most common question from new GST registrants. GSTR-1 and GSTR-3B serve completely different purposes in the GST return ecosystem, and understanding the distinction is critical to avoiding notices, mismatches, and ITC problems.

This guide explains what each return contains, when to file them, how they relate to each other, and what happens when they don't match.

GSTR-1: The Sales Return

GSTR-1 is your outward supply statement — a complete record of every sale you made during the month (or quarter, for QRMP taxpayers). It includes:

What Goes in GSTR-1

• Table 4: B2B invoices (to registered dealers) — invoice-level detail with buyer GSTIN
• Table 5: B2B invoices to URP (unregistered persons) for inter-state sales >₹2.5 lakh
• Table 6: Zero-rated/deemed exports
• Table 7: B2C (large) — inter-state sales to unregistered persons >₹2.5 lakh
• Table 8: B2C (others) — consolidated intra-state sales to unregistered persons
• Table 9: Amendments to B2B invoices of earlier periods
• Table 11: Advance received and adjusted
• Table 12: HSN summary of outward supplies

Why GSTR-1 Matters

Your GSTR-1 directly determines your buyers' ITC. When you report an invoice in Table 4 (B2B), it appears in your buyer's GSTR-2B within days. If you don't file GSTR-1 or miss an invoice, your buyer cannot claim ITC on that purchase.

GSTR-3B: The Payment Return

GSTR-3B is your monthly self-assessment return. It was introduced as a "temporary" return in July 2017 and has become permanent. Unlike GSTR-1, it only has summary numbers:

What Goes in GSTR-3B

• Table 3.1: Outward supplies — total taxable value and tax (not invoice-level)
• Table 3.2: Inter-state supplies to unregistered persons and composition dealers
• Table 4: ITC claimed — eligible, reversed, ineligible, net ITC
• Table 5: Exempt, nil-rated, and non-GST supplies
• Table 6.1: Tax payable and tax paid (cash + ITC offset)

Why GSTR-3B Matters

This is where you actually pay tax to the government. The system auto-populates some values from GSTR-1 and GSTR-2B, but you can edit them. Tax is offset against ITC balance and the remaining is paid via electronic cash ledger.

How GSTR-1 and GSTR-3B Connect

The GST system constantly cross-references these two returns:

1. Your GSTR-1 outward supply should equal GSTR-3B Table 3.1(total output tax). Any difference triggers DRC-01B auto-notice.
2. Your GSTR-1 Table 4 (B2B) feeds into buyer's GSTR-2B, which the buyer uses to fill GSTR-3B Table 4 (ITC).
3. GSTR-3B Table 4 ITC is compared against GSTR-2B auto-populated ITC. Excess claims trigger notices.

Common Mismatches and How to Avoid Them

1. GSTR-1 shows more sales than GSTR-3B

Problem: You reported invoices in GSTR-1 but paid less tax in GSTR-3B.

Fix: This usually means you forgot to include some invoices in GSTR-3B Table 3.1. Pay the differential tax with interest via DRC-03.

2. GSTR-3B shows more sales than GSTR-1

Problem: You paid tax on supplies not reported in GSTR-1.

Fix: Amend GSTR-1 in the next period to include the missing invoices. Your buyer is probably unable to claim ITC until you do this.

3. Credit notes in GSTR-1 not reflected in GSTR-3B

Problem: You reported credit notes in GSTR-1 Table 9 but didn't reduce output tax in GSTR-3B.

Fix: Adjust in the next GSTR-3B, or file with adjusted values going forward. This is over-payment (not under-payment), so no penalty, but you lose cash flow.

4. B2B invoice missing from GSTR-1

Problem: Your buyer sees ITC in GSTR-2B as "missing" because you didn't report in GSTR-1.

Fix: Report the invoice in next period's GSTR-1 (it will then appear in buyer's GSTR-2B).

Filing Sequence and Dependency

1. IFF (Invoice Furnishing Facility) — QRMP taxpayers upload B2B invoices monthly (optional but recommended)
2. GSTR-1 — Must be filed before GSTR-3B (mandatory since Jan 2022)
3. GSTR-3B — Filed after GSTR-1, with auto-populated values from GSTR-1 and GSTR-2B

QRMP vs Monthly Filing

Reconciliation Checklist

Run this reconciliation every month before filing GSTR-3B:

1. Match GSTR-1 Table 4+5+6+7+8 total with GSTR-3B Table 3.1(a) taxable value
2. Match GSTR-2B ITC with GSTR-3B Table 4 ITC claimed
3. Verify credit notes in GSTR-1 Table 9 are reflected as reduced output in GSTR-3B
4. Check advances received (GSTR-1 Table 11) against GSTR-3B treatment
5. Reconcile tax paid in GSTR-3B Table 6 with electronic credit/cash ledger balances