Difference between GSTR-1 and GSTR-3B, their monthly and quarterly due dates, and how to reconcile both with GSTR-2B before filing to avoid ITC loss and ASMT-10 notices.
Most GST trouble — ASMT-10 notices, blocked credit, working-capital crunches — traces back to one root cause: not understanding how GSTR-1, GSTR-3B and GSTR-2B fit together. This article unpacks the monthly cycle in plain language, with examples, deadlines and the reconciliation playbook used by audit-grade firms. If monthly filing keeps slipping, our GST return filing service handles GSTR-1, 3B and 2B reconciliation for you.
| Return | What it reports | Frequency | Due date |
|---|---|---|---|
| GSTR-1 | All outward supplies (sales invoices) | Monthly / Quarterly (QRMP) | 11th of next month / 13th |
| GSTR-3B | Summary return — tax payable + ITC claimed | Monthly / Quarterly | 20th of next month / 22nd or 24th |
| GSTR-2B | Auto-drafted ITC statement (suppliers' GSTR-1) | Monthly (auto) | Generated 14th |
Your supplier's GSTR-1 becomes your GSTR-2B. Your GSTR-1 becomes your buyer's GSTR-2B. Your GSTR-3B is the actual tax payment — but it MUST match the ITC available in your GSTR-2B and the output declared in your GSTR-1. Any drift between these three is exactly what the GST department's risk engine looks for.
Lock invoice numbering by the 5th. The longer you allow back-dated entries, the more reconciliation breaks the following month.
Quarterly Return Monthly Payment lets you file GSTR-1 and GSTR-3B quarterly while paying tax monthly using PMT-06. You also get the IFF (Invoice Furnishing Facility) to upload B2B invoices in the first two months of a quarter, so buyers can claim ITC without waiting for your quarterly GSTR-1. This is the right default for most SMBs.
Never claim 'provisional' ITC on the hope that the supplier will file later. Since Rule 36(4) was tightened, 100% of claimed ITC must reflect in GSTR-2B at the time of filing GSTR-3B.
| Default | Penalty |
|---|---|
| Late GSTR-1 | ₹50/day (₹20 nil), capped at ₹10,000 per return |
| Late GSTR-3B | ₹50/day (₹20 nil) + 18% p.a. interest on tax outstanding |
| GSTR-1 not filed before 3B | GSTR-3B blocked from filing (sequential rule) |
| Six months of non-filing | Suo-motu cancellation under Rule 21 |
False. Even a nil return must be filed every month. Six consecutive nil returns can trigger cancellation.
Partly true — corrections are allowed up to 30th November of the next financial year. But credit notes and amendments have separate fields; you cannot just delete the original.
Dangerously wrong. GSTR-1 is what your buyer relies on for ITC. Skipping it kills your client relationships before the department even notices.
GST is a self-policing system: every invoice you issue lands in your buyer's 2B, and every invoice you receive should land in yours. Treat the monthly cycle as a discipline — file on time, reconcile before filing, and never let the books drift more than 30 days behind. Do that and you'll never see an ASMT-10.
Senior contributor at Taxpex Consultancy. Reviewed by a practising Chartered Accountant. Published on 2 May 2026 · Updated on 2 May 2026.
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