The two returns every regular GST filer submits each month confuse nearly everyone at first: GSTR-1 and GSTR-3B. They cover the same period, draw from the same invoices, and yet serve completely different purposes. Mixing them up — or letting them disagree — is one of the most common reasons small businesses receive mismatch notices.
GSTR-1: the invoice-level detail
GSTR-1 is your statement of outward supplies — every B2B sales invoice you issued in the period, reported individually: buyer GSTIN, invoice number, date, value, tax. It is due by the 11th of the following month (or quarterly if you are on QRMP).
It does two jobs at once: it reports your sales to the department, and it populates your buyers’ GSTR-2B — which is the data they use to claim ITC. A late or wrong GSTR-1 hurts your customers directly, which is why B2B buyers notice suppliers who file late.
GSTR-3B: the summary where you pay
GSTR-3B is a self-declared summary return: total outward liability, total eligible ITC, and the net tax you pay in cash. Due by the 20th of the following month (22nd/24th for quarterly QRMP filers, by state).
| GSTR-1 | GSTR-3B | |
|---|---|---|
| What it is | Invoice-wise sales details | Consolidated summary return |
| Due date | 11th | 20th |
| Contains | Every B2B invoice line | Totals: liability, ITC, net payable |
| Tax payment | No | Yes — cash ledger via PMT-06 |
| Feeds | Your buyers’ GSTR-2B | Your liability + ITC ledger |
| Late fee | ₹50/day (₹20 nil) | ₹50/day (₹20 nil) + 18% interest on tax |
Why mismatches trigger notices
The portal cross-checks the two returns automatically. If the liability in your GSTR-3B is lower than the sales you declared in GSTR-1, the system flags the gap under Rule 88C and you get a notice to explain or pay the difference — with interest accruing meanwhile.
Common causes of genuine mismatches:
- An invoice amended in a later month’s GSTR-1 but never adjusted in 3B.
- Credit notes reported in one return but missed in the other.
- Manual entry errors when totals are typed in by hand.
File GSTR-1 first, then file GSTR-3B from the same data. The order is not just a convention — it is how you guarantee the two returns can never contradict each other.
The monthly rhythm
- 1st–10th: finalize sales invoices for the month; issue credit notes.
- By 11th: file GSTR-1.
- 14th: GSTR-2B generates — reconcile purchases for ITC.
- By 20th: compute net liability, pay via PMT-06, file GSTR-3B.
Muneem produces both returns from the same invoice ledger — GSTR-1 invoice detail and GSTR-3B summary tables in Circular 170 format — so the two filings match by construction, and ITC comes pre-reconciled against your 2B upload.
