What gets filed, and why two returns instead of one
GSTR-1 is a detailed, invoice-level report of everything sold during the period — it's what your customers' GSTR-2B is built from, so an error or delay here doesn't just affect you, it affects every registered customer trying to claim input tax credit on your invoices. GSTR-3B is a summary return: total outward and inward supplies, tax liability, input tax credit claimed, and the actual tax payment. The two are meant to reconcile with each other, and increasingly, mismatches between them are exactly what draws departmental attention.
Since Section 16(2)(aa), input tax credit can only be claimed to the extent it appears in your GSTR-2B — auto-generated from your suppliers' GSTR-1 filings. This makes the whole system interdependent: a supplier who files late or incorrectly directly affects their customers' ability to claim credit, which is one of the reasons chasing supplier compliance has become a routine part of GST management for many businesses.
Monthly filing compared with the QRMP scheme
| Feature | Monthly filing | QRMP scheme |
|---|---|---|
| Eligibility | Any regular taxpayer | Turnover up to ₹5 crore in the preceding financial year |
| GSTR-1 frequency | Monthly | Quarterly, with an optional Invoice Furnishing Facility (IFF) to upload B2B invoices in the first two months |
| GSTR-3B frequency | Monthly | Quarterly |
| Tax payment | Monthly, with the return | Monthly, even though the return itself is quarterly — via a fixed sum or self-assessment method |
| Best suited to | Higher-volume businesses, or those wanting simpler monthly reconciliation | Smaller businesses wanting fewer return filings, without giving up monthly cash flow visibility to customers via IFF |
Documents needed each filing period
- Sales register or invoice-level sales data for the period, including B2B, B2C, exports and credit/debit notes.
- Purchase register, for reconciliation against GSTR-2B.
- Details of any advances received where GST applies on advance receipt.
- E-way bills generated during the period, for consistency with invoices reported.
- Bank statements, for reconciling actual receipts against declared turnover where needed.
- Details of any reverse-charge transactions during the period.
The monthly return filing process
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Data collection and sales register finalisation
Sales data for the period is finalised, checked for completeness against invoices actually issued, and classified correctly by supply type (B2B, B2C, export, and so on).
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GSTR-1 preparation and filing
Invoice-level details are uploaded and filed by the due date — this is what generates your customers' GSTR-2B, so accuracy and timeliness here directly affects them, not only you.
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GSTR-2B reconciliation
Once GSTR-2B is generated for the period, purchase records are reconciled against it to confirm exactly how much input tax credit is actually available to claim.
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GSTR-3B preparation
Outward liability, eligible input tax credit (as confirmed by the GSTR-2B reconciliation), and any reverse charge liability are computed and populated into the summary return.
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Payment and filing
Any net tax payable is paid, and GSTR-3B is filed by its due date — a return cannot be filed without the corresponding payment being made first.
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Period-end review
Before moving to the next period, we check for anything that needs carrying forward or flagging — a credit note not yet issued, an unmatched invoice still pending from a supplier, or a reverse-charge item that needs confirmation.
Due dates and penalties
| Return | Due date |
|---|---|
| GSTR-1 (monthly) | 11th of the following month |
| GSTR-1 (QRMP, with optional IFF in the interim months) | 13th of the month following the quarter |
| GSTR-3B (monthly) | 20th of the following month |
| GSTR-3B (QRMP) | 22nd or 24th of the month following the quarter, by state group |
| CMP-08 (composition taxpayers) | 18th of the month following the quarter |
| Default | Consequence |
|---|---|
| Late filing of GSTR-1 or GSTR-3B | Late fee per day of delay (₹50/day for most cases, ₹20/day for nil returns), subject to a turnover-linked cap |
| Late payment of tax | Interest at 18% per annum on the tax paid late |
| Continued non-filing | Suspension and eventually cancellation of registration, and blocking of the e-way bill facility |
| Excess input tax credit claimed and later reversed | Interest at 24% per annum on the excess amount utilised |
Practical notes from our engagements
- ITC claimed before GSTR-2B confirms it. Since credit is only available to the extent it appears in GSTR-2B, claiming based on your own purchase register alone — before checking it against 2B — is one of the most common sources of a mismatch that surfaces later.
- Nil returns skipped because "there's nothing to report." A nil GSTR-3B is still a return, and still due — the ₹20/day late fee applies to a late nil filing just as it would to any other.
- QRMP monthly payment miscalculated. Even under QRMP, tax has to be paid monthly through the first two months of the quarter, using either a fixed-sum method or self-assessment — treating QRMP as "pay once a quarter" is a frequent and costly misunderstanding.
- Credit notes issued but not reflected in the return for the same period. A credit note raised against an earlier invoice needs to be reported in the period it's issued, and reconciled against the original invoice — leaving this until year end complicates both GSTR-1 accuracy and the eventual annual return.
- E-way bills and invoices drifting out of sync. Where e-way bills are generated but the corresponding sale isn't reported in the same period's GSTR-1, it's exactly the kind of discrepancy a departmental audit looks for.
How we handle the monthly return cycle
We reconcile purchase records against GSTR-2B before finalising the credit claimed in GSTR-3B, rather than relying solely on the client's own purchase register — this is where most avoidable disputes with the department originate. Filing itself is scheduled ahead of the due dates, not on them, so there's time to resolve a query with a supplier or a client before a deadline is actually at risk.
Related services
Frequently asked questions
What's the difference between GSTR-1 and GSTR-3B?
GSTR-1 is a detailed, invoice-level report of outward supplies, which feeds your customers' input credit. GSTR-3B is a summary return declaring total liability and making the tax payment. Both are filed for the same period, on different due dates.
Do I have to file a return if I had no sales or purchases in a period?
Yes — a nil return is still due. A late fee, though lower than for a return with activity, still applies if a nil return is filed late.
Am I eligible for the QRMP scheme?
If your aggregate turnover was up to ₹5 crore in the preceding financial year, you can opt into QRMP, filing GSTR-1 and GSTR-3B quarterly while still paying tax monthly.
Under QRMP, do I still need to pay GST every month?
Yes. QRMP reduces the number of returns filed, not the frequency of payment — tax is still paid monthly in the first two months of the quarter, using either a fixed-sum or self-assessment method.
Can I claim input tax credit that doesn't appear in my GSTR-2B?
No, not under current law — credit is available only to the extent it's reflected in GSTR-2B, which is generated from your suppliers' GSTR-1 filings. This is why supplier compliance affects your own credit position.
What happens if a supplier files their GSTR-1 late?
The corresponding credit won't appear in your GSTR-2B until they do, which can delay or reduce the credit you're able to claim for that period — a reason many businesses actively follow up with suppliers on filing status.
Is there a penalty for filing GSTR-1 late even if GSTR-3B is filed on time?
Yes, GSTR-1 and GSTR-3B are separate returns with separate late fees — filing one on time doesn't offset a delay on the other.
Can I switch between monthly filing and QRMP during the year?
The option is generally exercised at specific points the GST portal allows (typically at the start of a quarter), not switched arbitrarily mid-quarter — the exact window is confirmed on the portal each time.
What if I discover an error in a GSTR-1 I've already filed?
Most errors can be corrected in a subsequent period's return through amendment tables, rather than by refiling the original — though certain corrections have their own time limits worth checking against.
Does e-way bill generation need to match GSTR-1 exactly?
They should be consistent — invoices reported in GSTR-1 and the e-way bills generated for the same movements are compared during scrutiny, and unexplained gaps between them attract attention.