GSTR-1 is your sales statement: invoice by invoice, it tells the system and your buyers what you supplied. GSTR-3B is your tax return: a summary of sales, purchases and credit that works out what you owe and is where you actually pay. Both are filed for the same period, and the GST system now expects them to agree. Most notices small businesses receive about returns come from the gap between the two.
Side by side
| GSTR-1 | GSTR-3B | |
|---|---|---|
| What it is | Details of outward supplies (sales), under section 37 | Summary return with tax payment, under section 39 |
| Level of detail | Invoice-wise for sales to registered buyers; consolidated for most sales to consumers | Totals only |
| Who relies on it | Your buyers: their GSTR-2B (and so their credit) is built from it | You and the department: it settles your liability |
| Pays tax? | No | Yes, from the cash and credit ledgers |
| Monthly due date | 11th of the next month | 20th of the next month |
| Quarterly (QRMP) due date | 13th of the month after the quarter | 22nd or 24th of the month after the quarter, by State |
| Correcting it | GSTR-1A before 3B, or amendments in a later GSTR-1 | No revision. Adjust in a later return, or pay the difference separately |
The legal sources: section 37 and section 39 of the CGST Act, rule 59 for GSTR-1 and rule 61 for GSTR-3B. The 11th and 13th dates for GSTR-1 come from Notification No. 83/2020-Central Tax.
Both returns are due even in a month with no sales: section 39(8) requires a return for every tax period, and a nil return is still a return. If you would rather not track two sets of dates, our GST return filing service prepares and files both, with the credit check against GSTR-2B.
Monthly or quarterly: the QRMP choice
Businesses with aggregate turnover up to ₹5 crore in the previous financial year can opt for QRMP (quarterly return, monthly payment) under Notification No. 84/2020-Central Tax. You file GSTR-1 and GSTR-3B once a quarter, but tax is still paid each month: for the first two months of the quarter, by the 25th of the following month through a payment challan.
The quarterly GSTR-3B date depends on where your principal place of business is:
- 22nd of the month after the quarter: Chhattisgarh, Madhya Pradesh, Gujarat, Maharashtra, Karnataka, Goa, Kerala, Tamil Nadu, Telangana, Andhra Pradesh, and the UTs of Daman and Diu and Dadra and Nagar Haveli, Puducherry, Andaman and Nicobar Islands and Lakshadweep.
- 24th: all other States and UTs, including Delhi, Uttar Pradesh, Haryana, Punjab, Rajasthan, West Bengal and the north-eastern States.
If turnover crosses ₹5 crore during a quarter, you move to monthly filing from the first month of the next quarter.
IFF: monthly invoices for quarterly filers
A buyer can claim credit only once your invoice reaches their GSTR-2B. If you file quarterly, that can mean up to three months of waiting, which larger buyers dislike. The Invoice Furnishing Facility (IFF) fixes this. For the first and second months of a quarter, you can upload sales to registered buyers, up to ₹50 lakh a month, between the 1st and 13th of the next month. Invoices uploaded through IFF are not repeated in the quarterly GSTR-1. IFF is optional. Use it when your B2B buyers ask for it.
How the two returns are wired together
Three links matter more than anything else on this subject.
1. GSTR-1 feeds your GSTR-3B. The portal auto-fills the tax liability table in GSTR-3B from what you reported in GSTR-1 (and IFF or GSTR-1A). From the July 2025 tax period, the portal stopped letting you edit those auto-filled liability figures inside GSTR-3B. A correction now has to be made at the source, in GSTR-1A, before you file GSTR-3B for that period. GSTR-1A is an optional form, introduced in 2024 under rule 59, for amending or adding to a period’s GSTR-1 after filing it but before GSTR-3B.
2. GSTR-1 feeds your buyer’s credit. What you report becomes your buyer’s GSTR-2B. If you leave out an invoice or put it against the wrong GSTIN, your buyer either loses credit or gets it in the wrong month. Expect a phone call. Buyers now accept, reject or park supplier invoices on the portal’s Invoice Management System (IMS) before their own GSTR-3B. A rejected invoice comes back to you as something to fix.
3. The filing order is enforced. Under rule 59(6), you cannot file GSTR-1 (or IFF) for a period if GSTR-3B for the previous period is still pending. Under section 37(4), you cannot file GSTR-1 while an earlier GSTR-1 is still due. One missed return blocks the next.
What happens when they do not match
If the tax in your GSTR-1 is higher than the tax you paid through GSTR-3B by more than a set margin, rule 88C lets the portal send you an intimation in Form DRC-01B. You then have seven days to pay the difference with interest through DRC-03, or explain it. Until you respond, the portal blocks your next GSTR-1. Repeatedly declaring more sales in GSTR-1 than in GSTR-3B is also, under rule 21, a ground on which registration can be cancelled.
The reverse case, GSTR-3B higher than GSTR-1, does not trigger DRC-01B, but it still shows as a difference in your annual return and invites questions.
The usual causes of mismatch
- Invoices booked late. An invoice for 30 June entered after GSTR-1 was filed but counted in GSTR-3B. Fix it in GSTR-1A or the next GSTR-1, and do not shift the tax.
- Credit notes in one return only. Reported in GSTR-1 but not reduced in GSTR-3B, or the other way round.
- Advances. Tax paid in GSTR-3B on an advance received, with the invoice in GSTR-1 a month later. Keep a running schedule so it nets off.
- Wrong place of supply. An inter-State sale reported as intra-State, so IGST and CGST/SGST do not tie up even when the totals do.
- Amendments in GSTR-1 not carried into GSTR-3B for the period in which they were made.
- Rounding and HSN summaries that do not add up to the invoice table.
A five-minute habit prevents most of these. Before filing GSTR-3B, compare the GSTR-1 summary on the portal with your sales register for the period, and reconcile the credit you are about to claim against GSTR-2B.
Deadlines for fixing past periods
- GSTR-1 errors for a financial year can be corrected only until 30 November of the next year, or the date you file the annual return if that is earlier (section 37(3)).
- Old returns cannot be filed at all once three years have passed from their due date (sections 37(5) and 39(11)). The portal now enforces this. A return that is simply never filed eventually becomes impossible to file.
- Long gaps can lead to cancellation. A monthly filer who misses returns for six months in a row, or a quarterly filer who misses two quarters, is open to cancellation under rule 21.
Complianto (complianto.in), operated by Mentorcorp Private Limited, is a private consultancy and is not affiliated with any government body. We do not issue official documents. We charge a professional fee for application assistance and advisory services. Applicants can apply directly to the government without our fees via the official portals: MCA (mca.gov.in), Income Tax (incometax.gov.in), GST (gst.gov.in), MSME (udyamregistration.gov.in), FSSAI (foscos.fssai.gov.in), Startup India (startupindia.gov.in), and IP India (ipindia.gov.in).
This article is general information, not legal or tax advice.
