GSTR-1 Filing: What is GSTR-1 Form, Due Date & How to File Online (2026)

If you’re a GST-registered business in India, GSTR-1 is the return you’ll be dealing with most frequently. Every sale you make, every invoice you raise, every credit note you issue, it all gets reported here. Yet despite how central it is to GST compliance, a surprising number of businesses file it incorrectly, miss due dates, or don’t fully understand how their GSTR-1 affects their buyers’ ability to claim Input Tax Credit (ITC).

This article covers everything you need to know about the GST R-1 form, what it is, who files it, the exact due dates for FY 2025–26, a walkthrough of the form’s structure, and a step-by-step filing process.

Table of Contents

1. What is GSTR-1?
2. Who Needs to File GSTR-1?
3. GSTR-1 Due Date (2026), Monthly & Quarterly
4. GSTR-1 Form, Structure & Table Details
5. How to File GSTR-1 Online, Step by Step
6. GSTR-1 for QRMP Scheme Taxpayers
7. Common Mistakes to Avoid While Filing GSTR-1
8. Impact of GSTR-1 on Buyer’s Input Tax Credit
9. Frequently Asked Questions

What is GSTR-1?

GSTR-1 is a monthly or quarterly return that every GST-registered supplier must file to report all outward supplies, meaning all sales and services provided during the period. It is governed by Section 37 of the CGST Act, 2017.

Think of GSTR-1 as your sales register submitted to the GST department. It contains invoice-level details of every B2B sale, consolidated figures for B2C sales, credit and debit notes, advances received, and amendments to previously reported invoices.

The reason GSTR 1 is at the core of GST paradigm, even beyond just compliance, is that the data you report in your GSTR-1 directly flows into your buyers’ GSTR-2B, the auto-drafted ITC statement they use to claim ITC on purchases. If you file late or report incorrectly, your buyers suffer. That’s the kind of thing that damages business relationships quickly.

What is the Difference Between GSTR-1 and GSTR-3B?

This is one of the most common points of confusion for new filers. Both GSTR1 and GSTR3B, despite being monthly returns for common GST taxpayers, serve different purposes and are treated differently.

Feature	GSTR-1	GSTR-3B
Purpose	Report outward supplies (sales)	Summary return, pay tax liability
What it contains	Invoice-level details of all sales	Consolidated figures of sales, ITC, and tax payable
Nature	Statement of invoices	Self-assessed tax payment return
Revision	Cannot be revised; amend in next period	Cannot be revised after filing
Filing frequency	Monthly or quarterly	Monthly for all taxpayers
Effect on buyers	Populates buyer’s GSTR-2B for ITC	No direct impact on buyer

Despite their differences, both the returns are mandatory. GSTR-1 reports what you sold. GSTR-3B is where you calculate and pay the actual tax. Filing GSTR-1 without filing GSTR-3B (or vice versa) is incomplete compliance.

Who Needs to File GSTR-1?

All regular GST-registered taxpayers must file GSTR-1. This includes:

• Regular taxpayers (monthly or quarterly depending on turnover)
• SEZ units and SEZ developers
• Casual taxable persons (for the period of their registration)

The following are NOT required to file GSTR-1:

• Composition scheme taxpayers (they file CMP-08 and GSTR-4)
• Non-Resident Taxable Persons, they file GSTR-5
• Input Service Distributors, they file GSTR-6
• TDS deductors, they file GSTR-7
• TCS collecting e-commerce operators, they file GSTR-8
• Taxpayers under the OIDAR category, they file GSTR-5A

GSTR-1 Due Date (2026), Monthly & Quarterly

The due date for GSTR-1 depends on your annual turnover and whether you’re filing monthly or under the QRMP (Quarterly Return Monthly Payment) scheme.

Monthly filers: Taxpayers with aggregate annual turnover exceeding ₹5 crore in the previous financial year must file GSTR-1 every month.

Quarterly filers (QRMP): Taxpayers with aggregate turnover up to ₹5 crore can opt for the QRMP scheme and file GSTR-1 quarterly, while paying tax monthly via PMT-06.

GSTR-1 Due Date, Monthly Filers (FY 2025–26)

Tax Period	Due Date
April 2025	11 May 2025
May 2025	11 June 2025
June 2025	11 July 2025
July 2025	11 August 2025
August 2025	11 September 2025
September 2025	11 October 2025
October 2025	11 November 2025
November 2025	11 December 2025
December 2025	11 January 2026
January 2026	11 February 2026
February 2026	11 March 2026
March 2026	11 April 2026

Standard due date for GST R1 is 11th of the following month for monthly filers.

GSTR-1 Due Date, Quarterly Filers / QRMP (FY 2025–26)

Quarter	GSTR-1 Due Date	IFF (optional, M1 & M2) Due Date
Q1 (Apr–Jun 2025)	31 July 2025	13 May & 13 June 2025
Q2 (Jul–Sep 2025)	31 October 2025	13 August & 13 September 2025
Q3 (Oct–Dec 2025)	31 January 2026	13 November & 13 December 2025
Q4 (Jan–Mar 2026)	30 April 2026	13 February & 13 March 2026

The due date for GSTR1 for quarterly filers is 13th of the month following the quarter end (not the 11th, a common mistake).

What Happens if You Miss the GSTR-1 Due Date?

Missing the GSTR-1 due date triggers a late fee under Section 47 of the CGST Act. The fee is ₹50 per day (₹25 CGST + ₹25 SGST), but the maximum cap depends on your annual turnover:

Annual Turnover	Late Fee Per Day	Maximum Late Fee
Up to ₹1.5 crore	₹50/day	₹2,000
₹1.5 crore – ₹5 crore	₹50/day	₹5,000
Above ₹5 crore	₹50/day	₹10,000
Nil return (any turnover)	₹20/day	₹500

Beyond the fine, there’s a bigger practical consequence: your buyers cannot see your invoices in their GSTR-2B until you file. If you’re a significant supplier to a business, delaying your GSTR-1 directly blocks their ITC claims, which is something most business owners don’t fully appreciate until it becomes a client escalation.

GSTR-1 Form, Structure & Table Details

The GSTR-1 form isn’t a single page form, it’s a structured return with multiple tables, each capturing a different type of outward supply. Here’s what each section contains:

Table	What to Report
Table 4	B2B invoices, taxable supplies to registered persons (GSTIN mandatory)
Table 5	B2C large invoices, inter-state supplies to unregistered persons where invoice value exceeds ₹2.5 lakh
Table 6	Zero-rated supplies and deemed exports
Table 7	B2C small, all other B2C supplies (consolidated, state-wise)
Table 8	Nil rated, exempted, and non-GST outward supplies
Table 9	Amendments to B2B invoices of previous tax periods
Table 10	Amendments to B2C large invoices of previous periods
Table 11	Amendments to B2C small consolidated figures
Table 12	HSN-wise summary of outward supplies
Table 13	Documents issued during the period (invoices, credit notes, debit notes, revised invoices)

A Few Things Worth Knowing About Specific Tables

Table 4 (B2B) is the most critical, this is what populates your buyers’ GSTR-2B. Every GSTIN entered here must be active and valid. An invalid GSTIN causes that invoice to be rejected from the buyer’s ITC statement. To check any GSTIN validity, and current status, you can check the online GST number search tool, like one by ExpressGST.

Apart from Table 4, Table 12 (HSN Summary) is another important table, which became mandatory for all taxpayers from FY 2022–23. Taxpayers with turnover up to ₹5 crore must report HSN at 4-digit level; above ₹5 crore, 6-digit HSN is required.

Table 13 (Documents Issued) requires you to report the document number range, this helps the system track invoice sequence and flag gaps.

How to File GSTR-1 Online, Step-by-Step Process

GSTR-1 is filed on the official GST portal at gst.gov.in. Here is the complete step-by-step filing process:

Step 1: Log In to the GST Portal

Go to gst.gov.in → Login with your username and password → Dashboard appears.

Step 2: Navigate to GSTR-1

Services → Returns → Returns Dashboard → Select the financial year and return filing period → Click GSTR-1 → Prepare Online (or Prepare Offline if using offline tool / JSON upload).

Step 3: Add Invoice Details Table by Table

Fill in data for each applicable table:

• Add B2B invoices in Table 4 (with buyer GSTIN, invoice number, date, taxable value, tax rate, and tax amount)
• Add B2C large invoices in Table 5
• Add HSN summary in Table 12
• Add document summary in Table 13

For businesses with high invoice volumes, use the offline tool or direct API integration (like ExpressGST) to bulk upload data via Excel or JSON instead of manual entry.

Step 4: Save Each Table

Save each table as you go. The portal allows partial saving, you don’t need to complete everything in one session.

Step 5: Preview GSTR-1

Once all tables are filled → Click Preview GSTR-1 (PDF) to review the full draft return before submission. Check totals, GSTIN entries, and tax values carefully.

Step 6: Generate Summary and Submit

Click Generate GSTR-1 Summary → Review → Click Submit. Once submitted, the data is locked and flows into buyers’ GSTR-2B.

Step 7: File with EVC or DSC

• EVC (OTP), for proprietors, individuals, and partnerships
• DSC (Digital Signature), mandatory for companies and LLPs

After successful filing, an Acknowledgement Reference Number (ARN) is generated confirming your submission.

How to File GSTR-1 Using IFF (Invoice Furnishing Facility)

QRMP taxpayers have the option, not obligation, to use the Invoice Furnishing Facility (IFF) for the first two months of each quarter (M1 and M2). IFF lets you upload B2B invoice details monthly so your buyers’ GSTR-2B gets updated without waiting for the quarterly GSTR-1.

• IFF is optional, you are not penalised for not using it
• IFF due date: 13th of the following month for M1 and M2
• Only B2B invoices can be uploaded via IFF (not B2C)
• Invoices uploaded via IFF do not need to be reported again in the quarterly GSTR-1

If you have large B2B buyers who depend on monthly ITC credits, using IFF is a smart move that keeps your business relationships healthy.

How to Amend GSTR-1 After Filing

Once GSTR-1 is submitted, it cannot be revised or deleted. Mistakes are corrected in the next period’s GSTR-1 using the amendment tables (Tables 9, 10, 11).

To amend a B2B invoice from a previous period:

• Go to Table 9 in the current period’s GSTR-1
• Select the original invoice (it will auto-populate)
• Enter the corrected details
• The amendment flows into buyers’ GSTR-2B of the current period

Common amendments: wrong GSTIN, wrong invoice value, wrong tax rate, invoices reported in wrong period.

How to File Nil GSTR-1

If you had no outward supplies during a tax period, you must still file a Nil GSTR-1. You can do this via the portal in the usual way or, much faster, via SMS:

Send NIL R1 GSTIN TAX PERIOD to 14409

Example: NIL R1 27AABCU9603R1ZX 032026 (for March 2026)

You’ll receive a 6-digit OTP. Confirm by replying CNF R1 OTP. Done, no portal login needed.

GSTR-1 for QRMP Scheme Taxpayers

The QRMP (Quarterly Return Monthly Payment) scheme was introduced to reduce compliance burden for small taxpayers. Here’s how GSTR-1 works under QRMP:

Eligibility: Taxpayers with aggregate annual turnover up to ₹5 crore in the preceding financial year.

How it works:

• File GSTR-1 once per quarter (due by 13th of the month following the quarter)
• Pay tax monthly using Form PMT-06 (by 25th of each month)
• Optionally use IFF for M1 and M2 to share B2B invoice data with buyers monthly

Opting in/out of QRMP:

• You can opt in or out of QRMP between the 1st and 31st of the first month of any quarter
• QRMP selection is done at: Services → Returns → Opt-in for Quarterly Return

If your turnover exceeds ₹5 crore during the year, you must switch to monthly filing from the next quarter.

Common Mistakes to Avoid While Filing GSTR-1

There are some errors that show up repeatedly and either delay buyer ITC claims or attract scrutiny.

1. Entering an invalid or inactive GSTIN in Table 4

Every GSTIN in your B2B invoices is validated by the portal. An inactive or incorrect GSTIN means that invoice won’t appear in the buyer’s GSTR-2B, and they’ll chase you for it. Always verify before filing using a GST checker online tools.

2. Misclassifying B2B as B2C (or vice versa)

If a registered buyer’s invoice is reported under B2C (Table 7) instead of B2B (Table 4), the buyer won’t see it in their GSTR-2B and can’t claim ITC. This happens when the billing team doesn’t collect GSTINs from registered buyers.

3. Wrong HSN codes in Table 12

Incorrect HSN/SAC codes are one of the most common GSTR-1 errors. They cause mismatches in GSTR-9 (annual return) reconciliation and can invite notices.

4. Missing credit notes and debit notes

Credit notes issued to buyers must be reported in GSTR-1, they reduce the buyer’s ITC. Forgetting to report them means your GSTR-1 overstates your tax liability and the buyer’s GSTR-2B is inaccurate.

5. Reporting invoice numbers inconsistently

Invoice numbering must follow a consistent sequence. Gaps or duplicate invoice numbers in Table 13 are red flags during scrutiny.

6. Not using IFF for QRMP and blocking buyer ITC

QRMP taxpayers who skip IFF leave their B2B buyers without invoice visibility for two full months. If you have credit-sensitive B2B customers, this strains relationships, use IFF for M1 and M2.

7. Filing GSTR-1 after GSTR-3B

Ideally, GSTR-1 should be filed before or alongside GSTR-3B. Filing GSTR-3B first and then filing a GSTR-1 with significantly different numbers triggers system flags and may lead to a mismatch notice.

Impact of GSTR-1 on Buyer’s Input Tax Credit

This is the section most guides skip, and it’s arguably the most important reason to take GSTR-1 seriously.

When you file GSTR-1, the invoice data you report automatically populates your buyers’ GSTR-2B, the system-generated ITC statement. GSTR-2B is generated on the 14th of every month based on GSTR-1 data filed by suppliers up to that date.

Here’s what this means practically:

• If you file GSTR-1 by the 11th → your invoices appear in your buyer’s GSTR-2B on the 14th → buyer can claim ITC for that month
• If you file late (after the 14th) → your invoices appear in the next month’s GSTR-2B → buyer’s ITC is delayed by a full month
• If you report a wrong GSTIN → invoice doesn’t appear in the buyer’s GSTR-2B at all → buyer has to follow up with you

Under Rule 36(4) of the CGST Rules, buyers can only claim ITC on invoices that appear in their GSTR-2B. ITC on invoices not in GSTR-2B is now fully restricted. This makes your timely and accurate GSTR-1 filing a direct business obligation to your buyers, not just a tax compliance task.

Frequently Asked Questions on GSTR-1