If you run a GST-registered business in India, GSTR-1 is the one return you'll deal with more than any other. Every sale, every invoice, every credit note you issue — it all goes here. And yet, despite being at the centre of GST compliance, a surprising number of businesses file it wrong, miss due dates, or have no real idea how their GSTR-1 affects whether their buyers can claim Input Tax Credit.
This guide covers the full picture: what the GSTR-1 form actually is, who's required to file it, exact due dates for FY 2025–26, a breakdown of every table in the form, and a clear step-by-step process for filing online.
GSTR-1 is a monthly or quarterly return filed by every GST-registered supplier to report all outward supplies — meaning every sale and service provided during that period. It's governed by Section 37 of the CGST Act, 2017.
Think of it as your sales register, but submitted directly to the GST department. It carries invoice-level data for every B2B transaction, consolidated figures for B2C sales, credit and debit notes, advance receipts, and corrections to invoices from earlier periods.
What makes GSTR-1 different from other returns isn't just what it captures — it's what it triggers. The moment you file GSTR-1, the invoice data you've reported flows directly into your buyers' GSTR-2B, the auto-generated ITC statement they rely on to claim tax credit on purchases. File late or get something wrong, and your buyers pay the price. That's the kind of thing that quietly damages business relationships — and then loudly explodes once ITC claims start getting blocked.
GSTR-1 vs GSTR-3B: What's Actually Different
This is where most new filers get confused. Both returns are filed monthly by regular taxpayers, but they serve completely different purposes and work differently.
Feature
GSTR-1
GSTR-3B
Purpose
Reports all outward supplies (sales)
Summary return for paying actual tax liability
Contents
Invoice-level details of every sale
Consolidated sales, ITC, and tax payable
Nature
Sales statement
Self-assessed tax payment return
Can be revised?
No — amend in the next period
No — locked after filing
Filing frequency
Monthly or quarterly
Monthly for all taxpayers
Effect on buyers
Populates buyer's GSTR-2B for ITC
No direct effect on buyers
Both returns are mandatory. GSTR-1 tells the government what you sold. GSTR-3B is where you calculate and pay the actual tax. Filing one without the other is incomplete compliance — the system flags it.
Every regular GST-registered taxpayer must file GSTR-1. That covers:
The following categories are exempt — they file separate returns instead:
Your GSTR-1 due date depends on annual turnover and which filing scheme you're under.
Monthly filers — taxpayers whose aggregate annual turnover crossed ₹5 crore in the previous financial year must file every month.
Quarterly filers (QRMP scheme) — taxpayers with turnover up to ₹5 crore can opt into QRMP and file GSTR-1 quarterly, while making tax payments monthly through Form PMT-06.
Monthly GSTR-1 Due Dates (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 rule: the 11th of the following month, every time.
Quarterly GSTR-1 Due Dates / QRMP (FY 2025–26)
Quarter
GSTR-1 Due Date
IFF Due Date (M1 & M2, optional)
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
One thing quarterly filers get wrong constantly: the due date is the 13th of the month after the quarter ends — not the 11th. That's a GSTR-1 due date 2026 detail worth double-checking before each filing cycle.
GSTR-1 Late Fee Penalty 2026 — What It Actually Costs You
Missing the deadline triggers a late fee under Section 47 of the CGST Act. The fee structure:
Annual Turnover
Late Fee Per Day
Maximum Late Fee
Up to ₹1.5 crore
₹50/day
₹2,000
₹1.5 crore – ₹5 crore
₹5,000
Above ₹5 crore
₹10,000
Nil return (any turnover)
₹20/day
₹500
The fine matters — but the bigger consequence is practical. Your buyers can't see your invoices in their GSTR-2B until you file. If you're a significant supplier, a late GSTR-1 directly blocks their ITC claims for that month. For credit-sensitive buyers, this compounds fast.
GSTR-1 isn't a single form — it's a structured return with separate tables, each tracking a different type of outward supply.
Table
What Goes Here
Table 4
B2B invoices — taxable supplies to registered businesses (GSTIN required)
Table 5
B2C large invoices — inter-state supplies to unregistered buyers, invoice value above ₹2.5 lakh
Table 6
Zero-rated supplies and deemed exports
Table 7
B2C small — all other B2C supplies, consolidated by state
Table 8
Nil-rated, exempted, and non-GST outward supplies
Table 9
Amendments to B2B invoices from earlier tax periods
Table 10
Amendments to B2C large invoices from earlier 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/debit notes, revised invoices)
The Tables That Cause the Most Problems in Practice
Table 4 (B2B) is the most consequential table in the entire return. Every GSTIN you enter here gets validated by the portal. If a GSTIN is inactive or entered incorrectly, that invoice gets rejected from the buyer's GSTR-2B entirely — they won't see it, can't claim ITC on it, and will follow up with you. Always verify GSTINs before filing using an online GST search tool.
Table 12 (HSN Summary) became mandatory for all taxpayers from FY 2022–23. Turnover up to ₹5 crore: report HSN at the 4-digit level. Above ₹5 crore: 6-digit HSN is required. I won't pretend these codes are intuitive — most tax professionals keep a reference sheet nearby, and there's no shame in that.
Table 13 (Documents Issued) asks for the document number range from the period. This lets the system track invoice sequences and flag gaps — which is exactly why consistent invoice numbering matters so much.
GSTR-1 is filed at gst.gov.in. Here's the complete process.
Step 1: Log In to the GST Portal
Go to gst.gov.in → enter your username and password → your dashboard loads.
Step 2: Navigate to GSTR-1
Services → Returns → Returns Dashboard → choose the financial year and filing period → click GSTR-1 → select Prepare Online (or Prepare Offline if you're uploading via the offline tool or JSON).
Step 3: Fill In the Invoice Tables
Add data table by table:
For businesses with high invoice volumes, uploading via the offline tool or direct API integration using Excel or JSON saves significant time compared to manual entry.
Step 4: Save Each Table as You Go
The portal supports partial saving — you don't need to complete everything in one session. Save each table before moving to the next.
Step 5: Preview the Full Return
Once all tables are filled → click Preview GSTR-1 (PDF) → review the complete draft. Check all GSTIN entries, total taxable values, and tax amounts before proceeding. Catching errors here is far easier than amending after submission.
Step 6: Generate Summary and Submit
Click Generate GSTR-1 Summary → review once more → click Submit. At this point, the data is locked and begins flowing into buyers' GSTR-2B.
Step 7: File with EVC or DSC
After successful filing, an Acknowledgement Reference Number (ARN) is generated — this confirms your submission.
How to File GSTR-1 Using IFF (Invoice Furnishing Facility)
QRMP taxpayers have the option — not the obligation — to use IFF for the first two months of each quarter (M1 and M2). IFF lets you upload B2B invoice details monthly so buyers' GSTR-2B gets updated without waiting for the quarterly GSTR-1.
Key things to know:
If you have B2B buyers who depend on monthly ITC credits, using IFF is simply good business practice. Skipping it means their books are incomplete for two months.
How to Amend GSTR-1 After Filing
Once you submit, you can't revise or delete anything. Corrections go into the next period's GSTR-1 through the amendment tables.
To fix a B2B invoice from an earlier period:
The amendment then appears in your buyers' GSTR-2B for the current period. Common reasons for amendments: wrong GSTIN, incorrect invoice value, wrong tax rate, invoices filed under the wrong period.
How to File a Nil GSTR-1
Had zero outward supplies for the period? You still need to file. The fastest way isn't through the portal — it's SMS:
Send: NIL R1 [GSTIN] [TAX PERIOD] to 14409 Example: NIL R1 27AABCU9603R1ZX 032026 (for March 2026)
You'll get a 6-digit OTP. Reply with CNF R1 [OTP]. Done — no login required.
The QRMP (Quarterly Return Monthly Payment) scheme cuts the compliance load for smaller taxpayers. Here's how GSTR-1 works within it.
Who qualifies: Taxpayers with aggregate annual turnover up to ₹5 crore in the preceding financial year.
How the filing cycle works:
Opting in or out: You can switch between QRMP and monthly filing between the 1st and 31st of the first month of any quarter. To opt in: Services → Returns → Opt-in for Quarterly Return on the GST portal.
If your turnover crosses ₹5 crore during the year, you're required to move to monthly filing from the next quarter — not the next year.
These aren't edge cases — they're patterns that show up constantly, and most of them have a direct impact on your buyers.
Mistake 1: Invalid or Inactive GSTINs in Table 4
Every GSTIN in your B2B invoices gets validated at the portal level. An inactive or incorrectly entered GSTIN means that invoice is invisible in your buyer's GSTR-2B — they can't claim ITC on it. Always run GSTINs through an online GST checker before filing.
Mistake 2: Reporting a Registered Buyer Under B2C
When a buyer with a GSTIN gets their invoice filed under Table 7 (B2C) instead of Table 4 (B2B), it doesn't appear in their GSTR-2B. They can't claim ITC. This happens when the billing team doesn't collect GSTINs at the time of invoicing — an operational gap that creates a tax problem downstream.
Mistake 3: Wrong HSN Codes in Table 12
Incorrect HSN or SAC codes cause reconciliation mismatches in GSTR-9 (the annual return) and can attract notices. This is one of the most frequent errors, partly because the codes aren't always obvious. Keep a reliable HSN reference handy — it saves time and scrutiny later.
Mistake 4: Missing Credit Notes and Debit Notes
Credit notes issued to buyers reduce their ITC. If you don't report them in GSTR-1, your return overstates your tax liability and the buyer's GSTR-2B is inaccurate. Both sides lose. Report every credit and debit note in the period they're issued.
Mistake 5: Inconsistent Invoice Numbering
Invoice numbers must follow a consistent sequence. Gaps or duplicate numbers in Table 13 are red flags when your return gets reviewed. Build invoice numbering discipline into your billing process — not just into your filing process.
Mistake 6: QRMP Taxpayers Skipping IFF and Blocking Buyer ITC
If you're on QRMP and skip IFF for M1 and M2, your B2B buyers have no invoice visibility for two full months. For businesses that manage cash flow tightly against ITC credits, this creates real financial strain. Use IFF if you have credit-sensitive B2B customers.
Mistake 7: Filing GSTR-3B Before GSTR-1
GSTR-1 should be filed first, or at least alongside GSTR-3B. Filing GSTR-3B ahead with numbers that don't match a later GSTR-1 creates a system flag and can result in a mismatch notice. Get the sequence right.
Most guides treat this as an afterthought. It shouldn't be.
When you file GSTR-1, the invoice data flows automatically into your buyers' GSTR-2B — the system-generated ITC statement. GSTR-2B gets generated on the 14th of every month, pulling from GSTR-1 data that suppliers filed up to that date.
Here's what the timeline actually looks like in practice:
I've watched the third scenario turn into a serious client escalation by the second or third month in a row — once a buyer's working capital is affected, it moves beyond a tax issue quickly.
Under Rule 36(4) of the CGST Rules, buyers can only claim ITC on invoices that appear in GSTR-2B. ITC on invoices not showing up there is fully restricted — no exceptions, no workarounds. Your timely, accurate GSTR-1 filing is a direct commercial obligation to the businesses you sell to, not just a regulatory checkbox.
How do I file GSTR-1 online without making errors?
Log in at gst.gov.in → Services → Returns → Returns Dashboard → select your period → open GSTR-1 → fill tables starting with Table 4 for B2B invoices. Before submitting, use the Preview PDF to check all GSTINs, taxable values, and tax amounts. For high-volume businesses, the offline tool or JSON upload cuts down on manual entry errors significantly. Validate every GSTIN before you file — that single step prevents the most common and most damaging mistake.
What is the GSTR-1 due date for FY 2025–26?
Monthly filers must file by the 11th of the following month — so April 2025 is due by 11 May, and so on. QRMP (quarterly) filers have until the 13th of the month after the quarter ends: 31 July 2025 for Q1, 31 October 2025 for Q2, 31 January 2026 for Q3, and 30 April 2026 for Q4.
Can GSTR-1 be revised after it's filed?
No — once submitted, GSTR-1 is locked. There's no revision option. Corrections go into the amendment tables (Tables 9, 10, and 11) in the next period's GSTR-1. The amendment then shows up in your buyer's GSTR-2B for the current period. Common fixes include wrong GSTINs, incorrect invoice values, and invoices reported under the wrong tax period.
Who doesn't have to file GSTR-1?
Composition scheme taxpayers, Non-Resident Taxable Persons, Input Service Distributors, TDS deductors, TCS-collecting e-commerce operators, and OIDAR service providers are all exempt. They file their own specific returns — GSTR-4, GSTR-5, GSTR-6, GSTR-7, GSTR-8, and GSTR-5A respectively.
What is IFF in GSTR-1, and do I actually need to use it?
IFF (Invoice Furnishing Facility) is an optional monthly upload for QRMP taxpayers — specifically for the first two months of each quarter. It lets you share B2B invoice data with your buyers before the quarterly GSTR-1 is due. You're not penalised for skipping it. But if you have B2B buyers who depend on monthly ITC credits, using IFF keeps their books clean and your business relationship intact. The due date is the 13th of each of the first two months in a quarter.
What's the late fee for missing the GSTR-1 deadline?
₹50 per day for returns with supplies — ₹25 under CGST and ₹25 under SGST. The cap depends on your turnover: ₹2,000 for businesses below ₹1.5 crore, ₹5,000 for those between ₹1.5–5 crore, and ₹10,000 for above ₹5 crore. For nil returns, the fee drops to ₹20 per day up to ₹500. Beyond the fine, the practical consequence — blocking buyer ITC — is usually what matters more.
What happens if I enter a wrong GSTIN in GSTR-1?
That invoice won't appear in the buyer's GSTR-2B. They won't be able to claim ITC on it, and the portal won't alert either of you automatically. The fix is to amend the entry in Table 9 of the next period's GSTR-1 with the correct GSTIN. The corrected invoice then shows up in the buyer's GSTR-2B for that period. Always verify GSTINs before filing — an online GST search tool takes seconds and prevents this entirely.
GSTR-1 filing is monthly or quarterly — but the impact it has on your buyers is immediate. Get the date right, get the GSTIN right, and get it filed before the 11th. Everything else follows from those three habits.
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