By Taxabide 05 Oct 2026

GSTR-1 Filing in October 2026: Due Date, Rules & How to File

Published: October 5, 2026
Last Updated: October 5, 2026

Quick Answer

GSTR-1 Filing is the GST return process used by eligible registered taxpayers to report their outward supplies for the relevant tax period. For October 2026, monthly taxpayers generally file GSTR-1 for September 2026 by 11 October 2026, while QRMP taxpayers generally file the July–September 2026 quarterly GSTR-1 by 13 October 2026.

GSTR-1 is a statement of outward supplies in which businesses report relevant sales and invoice information to the GST system. The information can then be used for the recipient's GST compliance and input-tax-credit reconciliation.

Important: GST authorities can extend or change due dates through notifications or advisories. Check the official GST Portal before filing if any October 2026 update applies.

Key Takeaways

  • Monthly GSTR-1 for September 2026 is generally due on 11 October 2026.

  • QRMP taxpayers generally file quarterly GSTR-1 by 13 October 2026 for the July–September 2026 quarter.

  • GSTR-1 primarily reports outward supply details.

  • Correct invoice and customer information are important for GST reconciliation.

  • GSTR-1 and GSTR-3B serve different purposes.

  • GSTR-1A can be used as an optional amendment facility before filing GSTR-3B for the same tax period.

  • Late filing can attract applicable late fees.

  • Businesses should reconcile sales records before submitting GSTR-1.

What Is GSTR-1?

GSTR-1 is the GST statement used by eligible registered taxpayers to report details of their outward supplies of goods and services.

Depending on the transactions, the statement can contain information such as:

  • B2B supplies

  • B2C supplies

  • Export supplies

  • Credit and debit notes

  • Amendments to previously reported invoices

  • Other applicable outward-supply information

The official GST Portal provides an online and offline process for creating and filing GSTR-1 and allows taxpayers to add or amend outward-supply records before generating the final summary. 

GSTR-1 Filing October 2026: Due Dates

The applicable due date depends mainly on your filing frequency.

Taxpayer category

Tax period

Standard GSTR-1 due date

Monthly filer

September 2026

11 October 2026

QRMP quarterly filer

July–September 2026

13 October 2026

The GST Portal's QRMP guidance states that quarterly GSTR-1 is generally due on the 13th of the month following the quarter.

GSTR-1 Due Date for Monthly Filers

If your business files GSTR-1 monthly, the September 2026 outward-supply statement is generally due on 11 October 2026.

For example, if your business made taxable sales during September 2026, the applicable outward-supply details should be prepared and reported in the September GSTR-1.

GSTR-1 Due Date for QRMP Taxpayers

If your business has opted for the QRMP scheme and files GSTR-1 quarterly, the July–September 2026 quarter generally has a 13 October 2026 GSTR-1 due date. 

Businesses using the QRMP scheme should also understand the optional Invoice Furnishing Facility (IFF) for the first two months of the quarter. IFF can help eligible quarterly filers make invoice information available to recipients earlier. 

What Details Are Reported in GSTR-1?

GSTR-1 is primarily focused on outward supplies.

Depending on your business transactions, you may need to report:

  • GSTIN and invoice details of registered customers

  • B2B invoices

  • B2C supplies

  • Export invoices

  • Debit notes

  • Credit notes

  • Amendments to previously reported invoices

  • Applicable HSN/SAC-related information

  • Other prescribed outward-supply details

The exact tables applicable to your return depend on the nature of your transactions.

The GST Portal's filing guide also provides validation checks while preparing the GSTR-1 summary, helping identify inconsistencies between different tables. 

How to File GSTR-1 Online in October 2026

Step 1: Log in to the GST Portal

Open the official GST Portal and log in with your GST credentials.

Step 2: Open Returns Dashboard

Go to:

Services → Returns → Returns Dashboard

Select the applicable financial year, quarter, and month.

The official GST Portal provides this workflow for creating and filing GSTR-1. 

Step 3: Select GSTR-1

Open the GSTR-1 tile and choose whether to prepare the return online or use the applicable offline utility.

Step 4: Enter or Upload Sales Details

Add the relevant outward-supply information, including invoices, customer GSTINs, taxable values, tax amounts, and applicable amendments.

Step 5: Reconcile Your Data

Compare GSTR-1 information with:

  • Sales register

  • Tax invoices

  • Credit notes

  • Debit notes

  • E-invoice data, where applicable

  • Accounting records

Step 6: Generate Summary

Review the information and generate the GSTR-1 summary.

The GST Portal provides validation checks before the taxpayer proceeds to filing. 

Step 7: File GSTR-1

After checking the final figures, proceed with filing using the applicable authentication method.

Keep the filing acknowledgement for your GST compliance records.

GSTR-1 vs GSTR-3B: What's the Difference?

These two GST returns are connected but serve different purposes.

GSTR-1

GSTR-3B

Reports outward supplies

Reports summary GST liability and ITC

Contains invoice/supply details

Contains summary figures

Helps recipients reconcile purchases/ITC

Used to discharge applicable GST liability

Generally due earlier

Generally due after GSTR-1

For example, a monthly taxpayer may first prepare the September outward-supply information in GSTR-1 and subsequently use the relevant figures while preparing GSTR-3B.

TaxAbide's GST Return Filing service also identifies GSTR-1 as the return for outward supplies and GSTR-3B as the monthly summary return. Smart Tax Consultancy Services in India

What Is GSTR-1A?

GSTR-1A is an optional amendment facility introduced for correcting or adding certain records of the same tax period after GSTR-1 has been filed.

According to the official GST Portal, GSTR-1A becomes available after GSTR-1 is filed or its due date has passed, whichever is later, and it can be used before filing GSTR-3B for the same tax period.

This makes GSTR-1A useful when a taxpayer identifies an eligible omission or error before filing the corresponding GSTR-3B.

However, it should not replace careful reconciliation before the original GSTR-1 is filed.

GSTR-1 Late Fee

Late filing of GSTR-1 can attract a late fee under the applicable GST provisions and notifications.

The late-fee framework has been rationalised through government notifications, including different maximum amounts for certain taxpayer categories. CBIC's notification records specifically identify Notification No. 20/2021-Central Tax as the notification rationalising late fees for delayed GSTR-1 filing. CBIC GST

Therefore, businesses should not rely on a single generic late-fee figure without checking the applicable taxpayer category and current GST provisions.

The safest approach is to file GSTR-1 before the due date and verify the amount displayed by the GST Portal if a return is filed late.

Common GSTR-1 Filing Mistakes to Avoid

Incorrect GSTIN

Entering the wrong customer's GSTIN can cause invoice data to appear against the wrong recipient.

Wrong invoice number or date

Invoice numbers and dates should match the accounting records.

Missing credit or debit notes

Credit notes and debit notes should be reviewed before finalising the return.

Mismatch with sales records

The GSTR-1 figures should be reconciled with the business's sales register and accounting records.

Ignoring amendments

If a previously reported invoice needs correction, check the appropriate amendment provisions instead of creating an incorrect new entry.

Filing without reviewing the summary

Always check the generated summary before submitting the return.

GSTR-1 Filing for Small Businesses

Small businesses can reduce GST errors by maintaining a simple monthly reconciliation process:

Sales Register → Tax Invoices → GSTIN Check → Credit/Debit Notes → E-Invoice Data → GSTR-1 → Reconciliation → Filing

Preparing these records throughout the month is easier than collecting everything immediately before the deadline.

If the business has many invoices, B2B customers, amendments, or multiple GST registrations, professional GST return filing support can make the process easier.

TaxAbide provides GST Return Filing services for businesses and taxpayers.

GSTR-1 Filing in Dehradun

Businesses registered under GST in Dehradun follow the applicable GST return framework across India.

However, local businesses may still need professional help with:

  • Sales reconciliation

  • GSTR-1 preparation

  • Invoice reporting

  • Credit/debit note reporting

  • GSTR-1A corrections

  • GSTR-3B coordination

  • GST compliance records

For businesses with regular B2B transactions or a large volume of invoices, checking the return before submission can help reduce avoidable errors.

You can learn more about TaxAbide through the About Us page or contact the team through the Contact Us page.

Official Sources for GSTR-1 Compliance

The GST Portal provides the official workflow for creating and submitting GSTR-1, including online and offline preparation options. 

The official QRMP guidance states that quarterly GSTR-1 is generally due on the 13th of the month following the quarter and also explains the optional Invoice Furnishing Facility. 

The GST Portal also explains that GSTR-1A is an optional amendment facility that can be used before filing GSTR-3B for the same tax period. 

For the latest October 2026 filing status, taxpayers should check the official GST Portal for any notification, extension, or technical advisory.

Final Takeaway

GSTR-1 Filing October 2026 is an important GST compliance task for businesses reporting outward supplies.

For monthly filers, GSTR-1 for September 2026 is generally due on 11 October 2026. For QRMP taxpayers, the quarterly GSTR-1 for July–September 2026 is generally due on 13 October 2026. 

Before filing, reconcile your sales register, invoices, GSTINs, credit/debit notes, and other applicable outward-supply information. If an eligible error or omission is identified after GSTR-1, the optional GSTR-1A facility may provide a correction route before filing GSTR-3B for the same period.

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Frequently Asked Questions

For monthly filers, GSTR-1 for September 2026 is generally due on 11 October 2026. QRMP quarterly filers generally have a 13th-of-the-following-month due date.

For the July–September 2026 quarter, QRMP taxpayers generally have to file GSTR-1 by 13 October 2026.

Late filing can attract applicable late fees under GST provisions and notifications. The applicable amount can depend on the taxpayer category and current rules.

Eligible taxpayers can use GSTR-1A, an optional amendment facility, for the same tax period before filing the corresponding GSTR-3B.

Businesses can get professional GST compliance assistance through TaxAbide's GST Return Filing service.