GSTR-1 vs GSTR-3B: How the Two Main GST Returns Differ

Every regular GST taxpayer files two recurring returns: GSTR-1 and GSTR-3B. They overlap — both cover your sales — but they do different jobs, run on different dates and feed different parts of the system. Understanding how they connect is the easiest way to avoid mismatch notices.

This article compares the two side by side and explains how to keep them in step. For the filing steps of each, see the GSTR-1 filing guide and the GSTR-3B filing guide.

What is the basic difference between GSTR-1 and GSTR-3B?

GSTR-1 is a statement of outward supplies. It lists your sales invoice by invoice for registered buyers, and in summary for most retail sales. It does not involve any payment.

GSTR-3B is a summary return with payment. It shows total sales, total input tax credit and the net tax you pay. There is no invoice detail in it.

Put simply: GSTR-1 tells the system what you sold and to whom; GSTR-3B tells it how much tax you owe and pays it.

How do GSTR-1 and GSTR-3B compare at a glance?

Point	GSTR-1	GSTR-3B
Purpose	Report outward supplies	Declare summary, claim ITC, pay tax
Detail	Invoice-wise for B2B; summary for B2C	Totals only
Monthly due date	11th of next month	20th of next month
Quarterly (QRMP) due date	13th after quarter	22nd or 24th after quarter (state-wise)
Payment involved	No	Yes
ITC claimed	No	Yes (from GSTR-2B)
Effect on buyers	Feeds their GSTR-2B	None directly
Correction route	GSTR-1A (before 3B) or amendment tables later	Adjust in a later GSTR-3B; no revision
HSN summary	Yes (Table 12)	No
Nil return	Required	Required (SMS option for nil)
Late fee	Section 47	Section 47
Interest	No (no payment)	Section 50 on late tax

How does GSTR-1 now control GSTR-3B?

Originally the two returns were independent, which led to frequent mismatches: businesses reported sales in GSTR-1 but paid less in GSTR-3B, or the other way round. The system has tightened in stages:

1. Auto-population. GSTR-3B Table 3 started pre-filling from GSTR-1.
2. GSTR-1A. A new optional form lets you add or amend the current period's GSTR-1 after filing it but before GSTR-3B. Its figures also flow into GSTR-3B.
3. Hard-locking. From the July 2025 tax period, the outward liability auto-populated from GSTR-1, GSTR-1A or IFF cannot be edited in GSTR-3B.

The practical result: GSTR-1 is now the master record for your liability. If GSTR-1 is wrong, GSTR-3B will be wrong too unless you correct it through GSTR-1A in time.

What is the right filing sequence each month?

1. Close your sales books for the month — every invoice, credit note and debit note entered.
2. File GSTR-1 by the 11th (or IFF by the 13th for QRMP months 1 and 2).
3. Compare the filed GSTR-1 summary with your sales register.
4. If something is missing or wrong, file GSTR-1A — once only, before GSTR-3B.
5. Review IMS for supplier invoices and generate or recompute GSTR-2B.
6. Prepare GSTR-3B: check the locked liability, claim ITC, add reverse charge and reversals.
7. Pay any cash balance and file GSTR-3B by the 20th (or 22nd/24th for QRMP).

Worked example: catching a mismatch with GSTR-1A

A Kolhapur textile trader (monthly filer) files GSTR-1 for August 2026 on 10 September with taxable outward supplies of ₹8,40,000 at 5%: tax ₹42,000 (CGST ₹21,000 + SGST ₹21,000).

On 15 September, while preparing GSTR-3B, the accountant finds a B2B invoice of ₹60,000 (5%) that was entered in the books on 31 August but left out of the GSTR-1 upload.

Item	Taxable value	CGST	SGST
Original GSTR-1	₹8,40,000	₹21,000	₹21,000
Missed invoice added via GSTR-1A	₹60,000	₹1,500	₹1,500
Liability auto-filled in GSTR-3B	₹9,00,000	₹22,500	₹22,500

Because the liability is locked in GSTR-3B, the trader cannot simply type ₹9,00,000. Filing GSTR-1A first adds the invoice and the liability flows in correctly. The buyer sees this invoice in their GSTR-2B for the next period, as the portal FAQ explains for records added through GSTR-1A.

Had the trader filed GSTR-3B first, the ₹3,000 of tax would have been under-paid. It would then have to be declared in a later GSTR-1 and paid in a later GSTR-3B, with interest under Section 50 from the original due date.

Why do GSTR-1 and GSTR-3B still differ sometimes?

Even with locking, legitimate differences arise. Common reasons:

• Advances received. Tax on advances for services may be paid in GSTR-3B in one month and adjusted against invoices later.
• Amendments. An amendment in this month's GSTR-1 for an earlier month changes this month's net figures.
• Credit notes. Credit notes issued in a different month from the original invoice shift liability between periods. See credit note under GST.
• Period differences. An invoice dated 31 March reported in April's GSTR-1 shifts liability.

Keep a short monthly reconciliation sheet listing each difference and its reason. If a notice arrives months later, this sheet is your answer.

How do the two returns affect your customers?

Your registered buyers only see your sales through GSTR-1 (and IFF or GSTR-1A). Those records reach their GSTR-2B, and from there their IMS and GSTR-3B. If you file GSTR-1 late, their credit is delayed. If you mistype their GSTIN, they lose it.

GSTR-3B matters to buyers indirectly. Section 16 makes input tax credit conditional on the supplier actually paying the tax to the government. A supplier who files GSTR-1 but never pays through GSTR-3B puts their buyers' credit at risk. Buyers increasingly check supplier filing status before paying invoices, so timely filing of both returns is a commercial advantage as well as a legal duty. More on this in input tax credit rules.

What are the late consequences for each?

Both returns attract a daily late fee under Section 47 at notified reduced amounts until filed. Only GSTR-3B attracts interest, because only GSTR-3B involves payment. Both are covered by the three-year time bar: after three years from the due date, neither can be filed on the portal. Long gaps in either can also lead to restrictions such as blocking of e-way bill generation and, ultimately, action on the registration.

How do you build a monthly GSTR-1 vs GSTR-3B reconciliation?

A simple sheet with one row per month is enough for most small businesses. Columns that work well:

Column	Source
Taxable value as per books	Sales register
Taxable value as per GSTR-1 (incl. GSTR-1A, amendments)	Filed GSTR-1 summary
Taxable value as per GSTR-3B Table 3.1	Filed GSTR-3B
IGST / CGST / SGST as per GSTR-1	Filed GSTR-1 summary
IGST / CGST / SGST as per GSTR-3B	Filed GSTR-3B
Difference	Calculated
Reason	Your note (advance, amendment, cut-off)
Period in which it reverses	Your note

Steps to keep it current:

1. After filing GSTR-1, record its summary figures the same day.
2. After filing GSTR-3B, record its Table 3.1 figures.
3. Investigate any difference above a small tolerance immediately, while the month is fresh.
4. Mark each difference with the later period in which it will reverse, and tick it off when it does.
5. At year-end, the running total of unexplained differences should be zero before you prepare the annual return.

This sheet is also what a tax officer asks for first when a mismatch communication arrives, so keeping it monthly turns a stressful notice into a ten-minute reply.

What about ITC — does GSTR-1 affect that?

Your own GSTR-1 does not change your ITC. ITC comes from your suppliers' GSTR-1 filings, which reach you through GSTR-2B and the Invoice Management System. That matching is a separate exercise covered in GSTR-2B reconciliation. Keep the two reconciliations apart: GSTR-1 vs GSTR-3B is about your sales and liability; GSTR-2B vs purchase register is about your credit.

What does a simple monthly reconciliation sheet look like?

A Jalgaon furniture maker keeps a one-page sheet for each month:

Line	GSTR-1	GSTR-3B	Difference
Taxable B2B sales	₹18,40,000	₹18,40,000	₹0
Taxable B2C sales	₹3,10,000	₹3,25,000	₹15,000
Credit notes	₹40,000	₹40,000	₹0
Tax at 18% on net sales	₹3,79,800	₹3,82,500	₹2,700

The ₹15,000 gap traced back to one B2C invoice raised on the last day of the month that was keyed into the books but left out of GSTR-1. The fix is to include it, either through GSTR-1A before GSTR-3B is filed or in the next month's GSTR-1, and note the link on the sheet so the annual return lines up later.

Common mistakes

• Treating GSTR-3B as the "real" return and GSTR-1 as paperwork — GSTR-1 now drives liability.
• Filing GSTR-3B first and fixing GSTR-1 later.
• Using GSTR-1A casually: it can be filed only once per period.
• Reporting B2B sales as B2C to save time, which costs buyers their credit.
• Not reconciling month-end credit notes between the two returns.
• Ignoring small monthly differences that add up to a large annual gap in GSTR-9.

Who should own each return inside a small business?

In many small firms the owner, an in-house accountant and an outside consultant all touch the returns. Agree clearly who prepares GSTR-1, who checks it against the books, who takes IMS actions and who files GSTR-3B. Most mismatches come from hand-offs: one person files GSTR-1 from the billing system while another files GSTR-3B from a spreadsheet built separately. Using a single source for both — your invoice records — removes that gap.

Key takeaways

• GSTR-1 = invoice-level sales statement; GSTR-3B = summary, ITC and payment.
• File GSTR-1 first; GSTR-3B liability auto-fills from it and is locked.
• GSTR-1A is the single, once-per-period chance to fix the current period before GSTR-3B.
• Buyers depend on your GSTR-1 for credit and on your GSTR-3B for tax actually paid.
• Keep a monthly reconciliation of every difference and its reason.

Exporting GSTR-1 data directly from your billing records — as Billing Software by Betterwork does — removes most typing errors that cause the two returns to drift apart.

This guide is general information, not tax advice. Rules last checked on 20 October 2026; confirm with your tax professional for your situation.