GSTR-1 Filing Guide: Due Dates, Tables and Late Filing Rules (2026)

GSTR-1 is the statement in which a registered taxpayer reports every outward supply — sales invoices, credit and debit notes, and advances received. It is the single most important return for your customers, because everything filed here lands in their GSTR-2B and drives their input tax credit. This guide covers the table-wise contents, due dates for monthly and QRMP filers, HSN summary rules, and what happens when you file late.

What Goes Into GSTR-1

The form is organised table-wise, with each table capturing a distinct type of outward transaction. The categories you will use most often are:

B2B accuracy matters most, because registered buyers reconcile your invoices against their purchase register before claiming credit. Advances are easy to miss — tax on an advance is due in GSTR-1 for the month of receipt, not the month of invoicing.

GSTR-1 Due Dates in 2026

Even a period with no sales needs a nil GSTR-1. Skipping it locks the next period’s return and keeps your buyers waiting for credit, so always file nil rather than leave a period open.

HSN Summary: Digit Requirements by Turnover

The HSN summary table in GSTR-1 carries digit requirements tied to your aggregate annual turnover (AATO). Reporting the right level of detail avoids validation errors and scrutiny:

Use a genuine HSN for each line of business rather than a generic code, because mismatched or placeholder codes are a common trigger for notices and buyer-side queries. Our HSN code finder helps you pick the correct code before filing.

How GSTR-1 Reaches Your Buyer’s Credit

Once filed, your invoices flow into each buyer’s GSTR-2B, the static statement on which they claim input tax credit under Section 16(2)(aa). An invoice you miss or misreport does not merely delay your paperwork — it directly reduces the buyer’s credit until you correct it. That is why registered buyers chase their suppliers’ GSTR-1 filings, and why timely filing is a customer-service issue as much as a compliance one.

Under the QRMP scheme, a quarterly GSTR-1 could delay buyer credit by weeks, so the Invoice Furnishing Facility (IFF) lets you push B2B invoices, credit notes and export documents in the first two months of the quarter by the 13th. Documents not uploaded through IFF simply roll into the quarterly return, so nothing is lost.

Corrections and Amendments via GSTR-1A

Spot an error before filing GSTR-3B for the period? GSTR-1A lets you add or modify records of the current period so that GSTR-1 and GSTR-3B stay aligned. Once the period closes, corrections are made through the amendment tables of a subsequent GSTR-1 — there is no facility to revise a filed return outright.

Late Filing: Lock, Blocked E-Way Bills and Fees

• Sequential lock under Section 59(6): if GSTR-1 for a period is not filed, GSTR-1 for subsequent periods cannot be furnished until it is.
• E-way bill block: after two consecutive tax periods of non-filing, e-way bill generation is blocked for the defaulter.
• Late fee accrues for each day of delay, so the exposure compounds daily — estimate it before filing with our GST late fee calculator.

Build a monthly cut-off rhythm: close the sales register by the 5th, reconcile invoices and advances by the 8th, upload by the 10th, and keep the 11th as buffer. Businesses with heavy B2B volumes usually assign this to a GST consultant or an accounts team with clear checklist ownership.

Key Takeaways

• GSTR-1 is due by the 11th of the following month, or the 13th after the quarter for QRMP filers; IFF runs in the first two months of the quarter by the 13th.
• B2B and B2C-large supplies go invoice-wise; B2C small is rate-wise; advances and credit notes are reported alongside.
• HSN reporting: 6 digits mandatory above ₹5 crore AATO; 4 digits for B2B in the ₹1.5-5 crore band.
• Filed GSTR-1 feeds the buyer’s GSTR-2B and therefore their ITC.
• Non-filing locks future GSTR-1s under Section 59(6) and blocks e-way bills after two consecutive periods.

Frequently Asked Questions

Who must file GSTR-1?

Every regular registered person files GSTR-1 — monthly, or quarterly under the QRMP scheme. Composition dealers and non-resident taxable persons report their supplies through other forms.

Is GSTR-1 required if there were no sales?

Yes. A nil GSTR-1 must be filed for the period. Non-filing triggers the sequential lock and late fee just like any other period.

Can GSTR-1 be revised after filing?

No. There is no revision facility for GSTR-1. Errors in the current period can be corrected through GSTR-1A before filing GSTR-3B, and through amendment tables in later periods otherwise.

What is the difference between B2C large and B2C small?

B2C large covers inter-state supplies above ₹2.5 lakh per invoice to unregistered buyers, reported invoice-wise. All other B2C supplies are reported as a rate-wise summary by state.

When does my invoice appear in the buyer’s GSTR-2B?

After your GSTR-1 or IFF upload is filed and processed, the documents flow into the buyer’s GSTR-2B for the period. The buyer claims ITC based on those records.

What happens if I miss GSTR-1 for two consecutive months?

The Section 59(6) bar prevents you from filing later periods until the earlier one is filed, and e-way bill generation is blocked after two consecutive non-filed periods. Late fee also accrues daily until you file.

Disclaimer: Tax laws change frequently. Verify current rates and deadlines on the official portals (incometax.gov.in, gst.gov.in) or consult a qualified professional before acting.