GSTR-1 vs GSTR-3B: Key Differences, Due Dates and What Businesses Need to File

GSTR-1 is your detailed sales record: every outward invoice, credit note and debit note for the period, reported one by one. GSTR-3B is the summary return where you declare your total tax liability, claim input tax credit, and actually pay GST. You need both, in that order: GSTR-1 first, then GSTR-3B, because GSTR-3B's outward-supply figures are now pulled directly from what you reported in GSTR-1.

Think of GSTR-1 as the detailed record of what you sold. For every invoice you raised during the period, you report the buyer's GSTIN (for B2B), the invoice number, date, value, tax rate and tax amount, plus any credit notes, debit notes and amendments to earlier invoices. Larger B2C invoices get reported individually too; smaller ones are summarised. There's an HSN-wise summary as well, which is where getting your HSN and SAC codes right actually matters for this return specifically.

GSTR-1 doesn't involve any tax payment. It's a disclosure return: it tells the GST system (and, indirectly, your buyers) exactly what you sold and to whom, so the credit chain can work.

GSTR-3B is where the money moves. It's a consolidated summary: total outward tax liability, total eligible input tax credit, and the net tax you owe after adjusting one against the other. You pay that net amount when you file it, using your electronic cash and credit ledgers.

Unlike GSTR-1, GSTR-3B carries no invoice-level detail at all. It doesn't list which invoices made up your sales figure or which purchases fed your ITC claim. It's purely totals.

Yes. If you're a regular GST-registered taxpayer, GSTR-1 and GSTR-3B are both mandatory for every tax period, even a period with zero sales (as a nil return). They're not alternatives to each other; they report different things and one doesn't substitute for the other. A business that files only GSTR-3B without a matching GSTR-1 hasn't disclosed its outward supplies at all, whatever tax it's paid.

The two used to be filed somewhat independently, with GSTR-3B's figures editable by hand. That changed from the July 2025 tax period: the outward-liability tables in GSTR-3B are now auto-populated directly from GSTR-1 (and from the Invoice Furnishing Facility, where used) and locked against manual editing on the portal.

In practical terms, this means GSTR-1 has to be filed first, and it has to be accurate, because GSTR-3B will simply carry forward whatever GSTR-1 says. If you spot an error after filing GSTR-1 but before filing GSTR-3B for the same period, the fix is a separate return called GSTR-1A. It lets you amend that same period's figures in the window between the two filings, rather than editing GSTR-3B directly. Once GSTR-3B itself is filed, it can't be revised at all.

This change was formalised by GSTN Advisory No. 606, dated 7 June 2025, hard-locking the auto-populated Table 3 values in GSTR-3B from the July 2025 tax period (the return filed in August 2025) onward. This environment can't reach the GST portal directly to check the advisory text itself, but its number, date and effective period are reported consistently across multiple independent GST-compliance publications. Confirm the exact current behaviour on the portal if you're relying on this for a specific filing.

Most GST-registered businesses file monthly, but a business with aggregate turnover up to ₹5 crore in the preceding financial year can opt into the QRMP scheme (Quarterly Return, Monthly Payment): filing GSTR-1 and GSTR-3B quarterly while still paying tax every month through a simple challan.

These dates get extended by government notification often enough that hard-coding them as permanent would be misleading. Treat the table above as the general pattern, not a promise. Always check the current due date on the GST portal before you rely on it, especially around a festival period or after a system outage, when extensions are common.

Because GSTR-3B's outward figures now come directly from GSTR-1, an outright mismatch between the two is less common than it used to be, but it still happens through timing differences, a credit note issued late, or an error caught only after both returns are filed. When it does:

• Your buyers feel it first. A buyer's input tax credit flows from your GSTR-1 into their GSTR-2B. If your GSTR-1 is wrong or late, their credit is wrong or delayed, and that's usually the first place a mismatch surfaces.
• The department can flag a discrepancy notice. A gap between what GSTR-1 discloses and what GSTR-3B pays tax on can trigger a scrutiny notice asking you to explain or correct it.
• Late correction can mean late fee and interest. If reconciling a mismatch means you owed more tax than you paid on time, that shortfall can attract the same late fee and interest rules as any other delayed payment, see GST late fees and interest for exactly how that's calculated.

• Assuming GSTR-1 replaces GSTR-3B. They report entirely different things: filing a detailed GSTR-1 doesn't mean your tax liability has been declared or paid.
• Filing GSTR-3B before reconciling GSTR-1. Since GSTR-3B's outward figures now come from GSTR-1, filing GSTR-1 in a hurry, without checking it against your own sales register, carries straight through into the return that actually determines your tax payment.
• Missing invoices in GSTR-1. An invoice left out doesn't just understate your own turnover. It denies that buyer's input tax credit until you fix it, which is often how a customer first notices the omission.
• Trying to edit GSTR-3B directly instead of using GSTR-1A. The outward-liability fields are locked. If you catch an error before filing GSTR-3B, GSTR-1A is the correction route, not the GSTR-3B form itself.
• Ignoring the effect on your customer's ITC. A late or incorrect GSTR-1 doesn't just create a compliance problem for you. It's often the reason a B2B client's accounts team starts asking questions about your invoice.

A small consulting business issues ₹5,00,000 worth of invoices to business clients during a month, all at 18% GST, and has ₹40,000 of eligible input tax credit from its own expenses that period.

• In GSTR-1: every one of those invoices is reported individually (client GSTIN, invoice number, date, taxable value and tax amount), adding up to ₹5,00,000 of outward supplies and ₹90,000 of output tax.
• In GSTR-3B: that ₹90,000 output tax figure now flows in automatically from GSTR-1. The business separately declares its ₹40,000 of eligible ITC, arrives at a net liability of ₹50,000, and pays that amount to file the return.
• Why consistency matters: if one client's ₹1,00,000 invoice was left out of GSTR-1 by mistake, GSTR-3B's auto-populated liability understates the true figure by ₹18,000, and that client's own ITC claim for the invoice has nothing to match against on their end.

Illustrative figures for a single, straightforward month. A real month usually has more invoices, credit notes and prior-period adjustments feeding into both returns.