Contents
- Introduction: GSTR-1 in FY 2026-27 – What Has Changed?
- Overview of Key Changes Effective April 2026
- Who Must File GSTR-1 & Who Is Exempt
- Due Dates & Filing Frequency for FY 2026-27
- New Invoice & Document Number Series from April 2026
- Mandatory HSN Reporting in Table 12 & Table 13
- E-Invoicing Compliance Before Filing GSTR-1
- Invoice Management System (IMS) – Supplier's Key Obligations
- Table-Wise Points While Filing GSTR-1
- LUT for Exports – Fresh Filing for FY 2026-27
- Tobacco Goods – MRP-Based Tax Reporting (Feb 2026 Onwards)
- Who Is Most Impacted by These Changes
- Timeline of GSTR-1 Changes: 2017 to 2026
- Pre-Filing Checklist for GSTR-1 FY 2026-27
- You May Also Like
- Frequently Asked Questions (FAQs) on GSTR-1 FY 2026-27
- Conclusion
Introduction: GSTR-1 in FY 2026-27 – What Has Changed?
GSTR-1 is the monthly or quarterly return that every regular GST-registered taxpayer must file to report their outward supplies (sales). It forms the backbone of the GST compliance ecosystem — data filed in GSTR-1 directly flows into the buyer's GSTR-2A, GSTR-2B, and now the Invoice Management System (IMS). Getting GSTR-1 right has never been more consequential than in FY 2026-27.
From April 1, 2026, GST compliance has shifted from a post-filing scrutiny model to real-time, portal-enforced controls. Mistakes in GSTR-1 now directly block your buyers' ITC and can cascade into your own GSTR-3B liability.
FY 2026-27 introduces a cluster of significant changes: the 3-year permanent filing lock is now operational, HSN and document reporting in Tables 12 and 13 are mandatory, the Invoice Management System (IMS) makes every invoice a two-party responsibility, GSTR-1A enables post-filing corrections, and GSTR-3B values are now hard-locked from GSTR-1 data. This guide covers every point you must keep in mind while filing GSTR-1 this year.
Click to reveal a quick tip!
Upload invoices to the GST portal on a rolling basis throughout the month — not all at once on the 10th. This gives your B2B buyers time to review invoices in IMS and helps you spot errors before the filing deadline of the 11th.
Overview of Key Changes Effective April 2026
The GST Council and CBIC have introduced a series of amendments that directly affect how GSTR-1 must be filed in FY 2026-27. These changes span document numbering, HSN compliance, e-invoicing, IMS obligations, and hard portal controls on return filing.
Note: Several of these changes were technically effective from mid-FY 2025-26 (e.g., IMS from October 2024, Table 12/13 from May 2025) but are now fully enforced with no grace period in FY 2026-27.
Important: GSTR-3B values in Table 3 (outward supply liability) are now auto-populated and hard-locked from GSTR-1/GSTR-1A/IFF data effective July 2025. You cannot manually override these figures — accuracy in GSTR-1 is therefore mandatory.
| Change | Effective From | Impact on GSTR-1 Filer | Consequence of Non-Compliance |
|---|---|---|---|
| Fresh Invoice / Document Series | April 1, 2026 | New numbering series mandatory from first invoice of FY | Reconciliation errors; departmental scrutiny |
| 3-Year GSTR-1 Filing Lock | October 2022 (enforcement from FY 2025-26) | Cannot file returns older than 3 years from due date | Permanent non-compliance for old periods |
| Mandatory HSN in Table 12 (dropdown) | February 2025 | HSN selected via portal dropdown; auto-populates description | JSON validation errors; return not accepted |
| Table 13 – Document-wise reporting | May 2025 | Invoice series, debit/credit note series must be declared | Mismatch notices; ITC issues for buyers |
| Invoice Management System (IMS) | October 14, 2024 (fully enforced FY 2026-27) | Supplier must track buyer's accept/reject actions | Rejected credit notes increase supplier's GSTR-3B liability |
| GSTR-1A (Post-filing amendment) | July 10, 2024 (CGST Notification) | Errors correctable via GSTR-1A before GSTR-3B is filed | If missed, amendment only in next period's return |
| GSTR-3B Table 3 Hard-Lock | July 2025 tax period | GSTR-3B liability auto-filled from GSTR-1; not editable | Wrong GSTR-1 = wrong tax payment; interest and penalty |
| E-Invoicing (AATO > ₹5 Cr) | Already applicable; enforced FY 2026-27 | IRN mandatory; 30-day upload window for AATO > ₹10 Cr | Invoices invalid for ITC if IRN not generated in time |
| MRP-Based Tax on Tobacco Goods | February 1, 2026 | Tax computed on MRP, not selling price; manual field edit needed | Tax under-reporting; demand and penalties |
| LUT for Exports – Annual Renewal | April 1, 2026 | FY 2025-26 LUT expired; fresh Form RFD-11 required | IGST must be paid on exports; refund delay; cash flow loss |
Who Must File GSTR-1 & Who Is Exempt
Before diving into the filing mechanics, it is important to confirm whether your registration category requires GSTR-1 at all. The filing obligation is broad but not universal.
Mandatory Filers
Every registered person under the regular GST scheme is required to file GSTR-1 for every return period — even if there are zero transactions (nil return). The following categories must compulsorily file GSTR-1:
- Regular taxpayers registered under the normal scheme with any level of turnover (monthly or quarterly depending on turnover).
- SEZ units and SEZ developers reporting their outward supplies separately.
- E-commerce operators who are required to collect TCS under Section 52 of the CGST Act.
- Non-resident taxable persons (NRTP) registered in India who make taxable supplies.
- Casual taxable persons for the period of their temporary GST registration.
Note: Filing a nil GSTR-1 is mandatory even when there are no outward supplies in a tax period. You can file a nil return via SMS — type NIL (space) R1 (space) GSTIN (space) Tax Period and send to 14409.
Who Is Exempt from Filing GSTR-1
The following registered persons are not required to file GSTR-1 under the current GST law:
- Composition taxpayers — they file CMP-08 quarterly and GSTR-4 annually instead.
- Input Service Distributors (ISD) — they file GSTR-6.
- TDS deductors under Section 51 — they file GSTR-7.
- OIDAR service providers (Online Information and Database Access or Retrieval) who pay tax themselves under Section 14 of the IGST Act — they file GSTR-5A.
- UIN holders (Unique Identification Number) such as embassies — they file GSTR-11.
Due Dates & Filing Frequency for FY 2026-27
GSTR-1 due dates are determined by the taxpayer's aggregate annual turnover (AATO) in the preceding financial year (FY 2025-26). The two categories are monthly filers and quarterly filers under the QRMP scheme.
Monthly Filers (Turnover > ₹5 Crore in FY 2025-26)
If your aggregate turnover exceeded ₹5 crore in FY 2025-26, you must file GSTR-1 every month. The due date is the 11th of the following month. For example, outward supplies of April 2026 must be reported by May 11, 2026.
| Tax Period (Month) | GSTR-1 Due Date (Monthly) | Remarks |
|---|---|---|
| April 2026 | May 11, 2026 | First month of FY 2026-27 |
| May 2026 | June 11, 2026 | |
| June 2026 | July 11, 2026 | |
| July 2026 | August 11, 2026 | |
| August 2026 | September 11, 2026 | |
| September 2026 | October 11, 2026 | |
| October 2026 | November 11, 2026 | |
| November 2026 | December 11, 2026 | |
| December 2026 | January 11, 2027 | |
| January 2027 | February 11, 2027 | |
| February 2027 | March 11, 2027 | |
| March 2027 | April 11, 2027 | Last month of FY 2026-27 |
Note: If the due date falls on a public holiday, filing is generally allowed on the next working day. However, no assumption of extension should be made without an official CBIC notification. Always check the GST portal for official relaxations.
QRMP Quarterly Filers (Turnover ≤ ₹5 Crore in FY 2025-26)
Taxpayers with AATO up to ₹5 crore may opt for the QRMP (Quarterly Return Monthly Payment) scheme. Under QRMP, GSTR-1 is filed once a quarter. The Invoice Furnishing Facility (IFF) is available in months 1 and 2 of each quarter for uploading B2B invoice details so buyers can claim ITC without waiting for the quarterly filing.
| Quarter | IFF (Months 1 & 2) Due Date | GSTR-1 (Quarterly) Due Date |
|---|---|---|
| Q1: April–June 2026 | May 13 & June 13, 2026 | July 13, 2026 |
| Q2: July–September 2026 | Aug 13 & Sep 13, 2026 | October 13, 2026 |
| Q3: October–December 2026 | Nov 13 & Dec 13, 2026 | January 13, 2027 |
| Q4: January–March 2027 | Feb 13 & Mar 13, 2027 | April 13, 2027 |
3-Year Filing Lock – Critical Deadline
Introduced by Finance Act 2022 and now firmly in the enforcement phase, the 3-year lock means GSTR-1 returns cannot be filed after three years from the month's due date have elapsed. This is a hard, permanent restriction — the GST portal will not allow filing beyond this window under any circumstances.
Warning: March 2023 GSTR-1 could only be filed until April 11, 2026. From April 2026 onwards, month-by-month locking continues for subsequent older periods. If you have any unfiled GSTR-1 returns from FY 2022-23 or earlier, the window is either closed or closing very soon. Prioritise clearing these immediately.
New Invoice & Document Number Series from April 2026
One of the most common compliance errors at the start of every financial year is continuing the previous year's invoice numbering series into the new year. For FY 2026-27, the GST rules require every registered business to start a fresh, consecutive document number series from April 1, 2026.
This fresh series must apply to all of the following types of documents:
- Tax Invoices (B2B and B2C) — start a new series such as INV/2026-27/001.
- Debit Notes — new series separate from invoices is best practice.
- Credit Notes — must also follow a new series for FY 2026-27.
- Export Invoices — if LUT is filed, ensure the series reflects the new year.
- Revised Invoices (if any issued during the composition-to-regular transition) — new series required.
Important: Carrying forward the old series from FY 2025-26 creates reconciliation problems in GSTR-1 and can attract departmental scrutiny. Update your billing software (Tally, Busy, ERP, etc.) on the first day of the financial year — April 1, 2026 — before raising a single invoice.
For businesses integrated with e-invoicing, the Invoice Reference Number (IRN) is unique per invoice. Even if document numbers repeat across years (which they should not), the IRN keeps each invoice distinct on the portal. Still, a fresh series is both a legal requirement and a sound accounting practice.
Mandatory HSN Reporting in Table 12 & Table 13
Table 12 and Table 13 of GSTR-1 have undergone significant mandatory changes that are fully enforced in FY 2026-27. These changes were rolled out in phases and are now non-negotiable for all applicable taxpayers.
HSN Digit Requirements by Turnover (Table 12)
The number of HSN code digits you must report depends on your aggregate annual turnover. As of FY 2026-27, the requirement is as follows:
| Aggregate Annual Turnover (AATO) | Minimum HSN Digits Required | Applicable Since |
|---|---|---|
| Up to ₹5 Crore | 4-digit HSN Code | Phase 3: May 2025 period |
| Above ₹5 Crore | 6-digit HSN Code (minimum) | Phase 2: November 2022 period |
From February 2025 onwards, Table 12 of GSTR-1 requires HSN codes to be entered via a portal dropdown rather than typed manually. When you select an HSN code from the dropdown, the portal auto-populates the HSN description. You cannot enter free-text HSN codes anymore — the system validates against the official HSN master.
Common Error Alert: Using an incorrect or outdated HSN code that does not match the dropdown list will cause a JSON validation error and the return will not be accepted by the portal. Always cross-verify HSN codes in your ERP/billing software against the updated 2022 HSN Schedule before filing.
Table 13 – Document-Wise Reporting (Effective May 2025)
From the May 2025 return period, taxpayers must also populate Table 13 of GSTR-1/1A. This table captures the series-wise summary of all documents issued during the tax period, including:
- Tax Invoices (issued and cancelled)
- Revised Invoices
- Debit Notes
- Credit Notes
- Advance Payment Receipts (Vouchers)
- Payment Refund Vouchers
For each document series, you must report the total number of documents issued and the first and last document numbers of that series for the period. This data is used by the GST department to cross-check invoice continuity and detect missing invoice reporting.
E-Invoicing Compliance Before Filing GSTR-1
E-invoicing is directly linked to GSTR-1 — once an IRN (Invoice Reference Number) is generated on the Invoice Registration Portal (IRP), the invoice data is automatically pushed to your GSTR-1 on the GST portal. This means for e-invoice eligible businesses, a significant portion of GSTR-1 data is auto-populated.
The e-invoicing eligibility for FY 2026-27 is as follows:
- AATO > ₹5 Crore in FY 2025-26: E-invoicing is mandatory from April 1, 2026 for this business. Every B2B invoice, debit note, and credit note must have an IRN.
- AATO > ₹10 Crore: In addition to mandatory e-invoicing, there is a 30-day time limit to report invoices on the IRP from the date of the invoice. Invoices reported after this 30-day window are considered invalid for ITC purposes by the recipient.
Critical: If you are above ₹10 crore AATO and fail to report an invoice within 30 days on the IRP, that invoice will not generate a valid IRN. The buyer cannot claim ITC on it. This directly harms your business relationship and may result in payment disputes. Generate IRN on the day of invoice issuance itself.
For e-invoice filers, always verify the following before filing GSTR-1:
- Step 1: Reconcile all IRN-generated invoices with those appearing in the auto-populated GSTR-1 on the portal. Discrepancies may arise from cancelled IRNs or failed data pushes.
- Step 2: Manually add any invoices where e-invoicing is exempt (e.g., B2C large invoices, SEZ supplies with payment of tax) that would not be auto-populated.
- Step 3: Check that cancelled IRNs do not appear in GSTR-1. A cancelled IRN must not be reported as a valid invoice.
- Step 4: Confirm that the GSTIN, invoice date, taxable value, and tax amounts match exactly between the e-invoice and what appears in GSTR-1.
Invoice Management System (IMS) – Supplier's Key Obligations
The Invoice Management System (IMS) was introduced on October 14, 2024, and is now central to the GST compliance workflow for FY 2026-27. As a supplier filing GSTR-1, understanding IMS is critical — your buyers are now reviewing, accepting, or rejecting each invoice you upload, and their actions directly impact your GSTR-3B liability.
How IMS Works for the Supplier
When you save or submit an invoice in GSTR-1, IFF, or GSTR-1A, it immediately appears in your buyer's IMS dashboard. The buyer has three options — Accept, Reject, or Keep Pending. The workflow is as follows:
- Step 1 – You upload the invoice: Save and file your GSTR-1 with all B2B invoice details. The invoices appear in your buyer's IMS dashboard in near real-time.
- Step 2 – Buyer takes action: The buyer can Accept (ITC flows to their GSTR-2B), Reject (ITC does not flow; you are notified via IMS Supplier View), or Keep Pending (for one tax period maximum for specified records).
- Step 3 – You check Supplier View: Log in to the GST portal, go to Services > Returns > IMS > Outward Supplies to see actions taken by your buyers. A rejected invoice means you need to investigate and correct it.
- Step 4 – Handle rejections before next GSTR-1 due date: If your invoice is rejected, you can amend it using GSTR-1A (if GSTR-3B for that period is not yet filed) or use the amendment table in the next GSTR-1.
Note: The IMS Supplier View allows you to see what action each recipient has taken on every invoice you have uploaded in GSTR-1/IFF/GSTR-1A. Make it a habit to check this dashboard weekly, not just at month-end.
GSTR-1A – Amending Filed Invoices Before GSTR-3B
A significant relief introduced via CGST Notification dated July 10, 2024, is the GSTR-1A form. This is a once-per-period amendment window that allows a supplier to correct errors in their filed GSTR-1 before filing GSTR-3B for the same period.
Key points about GSTR-1A:
- GSTR-1A can be filed from the date GSTR-1 is filed up to the time GSTR-3B for the same period is filed.
- It allows upward or downward amendments to invoices, debit notes, credit notes, and other documents already reported in GSTR-1.
- Once GSTR-1A is submitted, the amended data flows to the buyer's IMS in the subsequent month's GSTR-2B (not the same month's).
- GSTR-1A is also the only channel for IMS-triggered corrections — if a buyer rejects your invoice and you agree with the rejection, amend via GSTR-1A.
Important: If you miss the GSTR-1A window (i.e., GSTR-3B is already filed), then corrections must be made in the amendment tables of the next period's GSTR-1. The amendment time limit is up to November 30 of the following financial year or before the annual return is filed, whichever is earlier.
Credit Notes & IMS Impact
Credit notes carry special complexity under IMS. When you issue a credit note and report it in GSTR-1, it reduces your output tax liability. However, if the buyer rejects that credit note in IMS, the portal reverses this reduction — your GSTR-3B liability increases back to the pre-credit-note level.
Practical implications for FY 2026-27:
- Communicate with your buyer immediately when you report a credit note in GSTR-1. Explain the reason so they do not reject it inadvertently.
- If your buyer rejects a credit note in IMS, check all vendor credit notes you have rejected in IMS as well — rejected vendor credit notes reduce your ITC and require corrective action in GSTR-3B.
- Do not issue a credit note for a wrong invoice and expect IMS to handle reconciliation automatically — the supplier-and-credit-note scenario is one of IMS's known challenge areas. Use GSTR-1A to correct the original invoice instead.
Table-Wise Points While Filing GSTR-1
GSTR-1 has 13 tables (sections). Each must be populated correctly. The following are the key points for each relevant table:
| Table No. | Content | Key Points for FY 2026-27 |
|---|---|---|
| Table 4 | B2B Invoices (Taxable) | Enter buyer's GSTIN correctly. Wrong GSTIN = buyer loses ITC. IRN auto-populated for e-invoice filers. Verify each entry against e-invoice data. |
| Table 5 | B2C Large Invoices (>₹2.5L, Interstate) | Mandatory for large inter-state B2C supplies above ₹2.5 lakh. PAN-level reconciliation possible. Ensure place of supply is correct. |
| Table 6 | Zero-Rated Supplies (Exports & SEZ) | Clearly distinguish between exports with IGST payment and exports under LUT (without IGST). Shipping bill / bill of export details are required. LUT must be valid for FY 2026-27. |
| Table 7 | B2C Small Invoices (Summarized) | State-wise summary. Ensure inter-state and intra-state categorisation is correct. Rate-wise breakup required. |
| Table 8 | Nil-Rated, Exempt & Non-GST Supplies | Often overlooked. Report nil-rated and exempt sales separately; aggregate of all such supplies including exempt under Schedule III. |
| Table 9 | Amendments to B2B Invoices (Previous Periods) | Use for correcting invoices from previous return periods. Time limit: up to November 30 of next FY or before GSTR-9, whichever is earlier. |
| Table 9B / 9C | Amendments to B2C Large / Exports | Same amendment time limit applies. Always record the original invoice details before entering amended details. |
| Table 10 | Debit Notes / Credit Notes (B2B) | Link each note to the original invoice number and date. IMS will track recipient's action on your credit notes — communicate with buyers proactively. |
| Table 11 | Advances Received (Tax Payable on Advance) | GST is payable on advances received for services (not goods as of current law). Report and adjust properly when invoice is issued against the advance. |
| Table 12 | HSN-Wise Summary of Outward Supplies | Use portal dropdown only (no manual entry). 4-digit HSN for AATO ≤₹5 Cr; 6-digit for AATO >₹5 Cr. Rate, taxable value, and tax amounts must match invoice totals. |
| Table 13 | Document-Wise Summary (Mandatory from May 2025) | Report first and last number of each document series issued during the period. Include invoices, credit notes, debit notes, and cancelled documents count. |
LUT for Exports – Fresh Filing for FY 2026-27
If your business exports goods or services, or supplies to Special Economic Zones (SEZ units or SEZ developers) without payment of IGST, a Letter of Undertaking (LUT) under Form RFD-11 is mandatory. The LUT is not a one-time formality — it must be renewed every financial year.
The LUT filed for FY 2025-26 expired on March 31, 2026. It is not valid for any invoice raised from April 1, 2026 onwards. Here is what you need to do:
- Step 1: Log in to the GST portal at gst.gov.in.
- Step 2: Go to Services > Refunds > Furnish Letter of Undertaking (LUT).
- Step 3: Select FY 2026-27, fill in the required details, attach the LUT declaration, and submit using DSC or EVC.
- Step 4: Once approved, your LUT reference number is valid for all zero-rated supplies from April 1, 2026 to March 31, 2027.
Warning: If you raise an export invoice without a valid LUT for FY 2026-27, you are required to pay IGST on that export. While you can claim a refund later, this creates cash flow strain and unnecessary compliance work. File the LUT before the first export invoice of the year. Ideally, file before April 1, 2026 itself.
Also note: From April 1, 2026, the minimum refund threshold of ₹1,000 for export refunds has been removed. Every valid refund claim, even a small one, will now be processed by the GST department. This is a taxpayer-friendly change — ensure all your pending export refund applications are filed.
Tobacco Goods – MRP-Based Tax Reporting in GSTR-1 (February 2026 Onwards)
For businesses dealing in notified tobacco and tobacco-related products, a specific change in GSTR-1 reporting has been effective from February 1, 2026. These goods are subject to RSP (Retail Sale Price / MRP) based valuation, which means GST is computed on the MRP printed on the product — not on the actual selling price.
The formula for computing GST in such cases is:
Tax Amount = (MRP × GST Rate%) / (100 + GST Rate%)
Taxable Value = MRP − Tax Amount
Example:
MRP = ₹500, GST Rate = 28%
Tax Amount = (500 × 28) / (100 + 28) = 14000 / 128 = ₹109.375
Taxable Value = ₹500 − ₹109.375 = ₹390.625
In GSTR-1, you must report the actual net sale value (commercial transaction value, not MRP) in the taxable value field, and manually enter the MRP-calculated GST amount in the tax fields. This requires overriding the portal's auto-calculated tax figure.
Applicable HSN chapters include 21 and 24 (tobacco, pan masala, cigarettes, etc.) and Chapter 2404 (products intended for inhalation). If you are in this trade, update your billing software and train your accounts team on this reporting method.
Who Is Most Impacted by These Changes in FY 2026-27
While all regular GST taxpayers are affected by the GSTR-1 changes, certain categories face significantly higher compliance risk this year.
| Category of Taxpayer | Key Risk Area in FY 2026-27 | Recommended Action |
|---|---|---|
| Businesses with AATO > ₹10 Crore | 30-day IRN upload deadline; GSTR-3B hard-lock from GSTR-1 data | Generate IRN same-day; reconcile e-invoice data with GSTR-1 before filing |
| Exporters and SEZ Suppliers | LUT expiry on March 31, 2026; IGST payable without valid LUT | Renew LUT (Form RFD-11) before April 1, 2026 every year |
| B2B Suppliers with Large Buyer Base | IMS — buyers rejecting invoices or credit notes; GSTR-3B liability impact | Monitor IMS Supplier View weekly; communicate with key buyers |
| Businesses with Pending Old Returns | 3-year lock closing permanently for older periods | Identify and file all GSTR-1 pending for periods before April 2023 immediately |
| MSMEs / Small Businesses (AATO ≤ ₹5 Cr) | Table 12 HSN dropdown now mandatory; Table 13 document summary required | Update billing software with correct 4-digit HSN codes; train accounts staff |
| Tobacco / Pan Masala Traders | MRP-based GST computation from February 2026 | Reconfigure billing software; manually override tax fields in GSTR-1 |
| Taxpayers Newly Crossing ₹5 Crore Turnover | Shift from quarterly to monthly GSTR-1; e-invoicing now mandatory | Switch to monthly filing regime; set up IRP integration before April 1, 2026 |
| QRMP Scheme Taxpayers | IMS actions needed on invoices appearing in quarterly GSTR-2B; IFF B2B upload discipline | Use IFF in months 1 and 2 to ensure buyers get ITC on time |
Timeline of GSTR-1 Changes: 2017 to FY 2026-27
Understanding how GSTR-1 has evolved helps appreciate where compliance stands today and what is likely next. Here is a brief timeline of key milestones:
| Year / Period | Key Change in GSTR-1 |
|---|---|
| July 2017 | GST launched; GSTR-1 introduced as monthly outward supply return for all taxpayers |
| January 2021 | QRMP scheme introduced; turnover threshold raised from ₹1.5 Cr to ₹5 Cr for quarterly filing |
| January 2022 | Mandatory ITC matching with GSTR-2B; no provisional ITC beyond 5% without GSTR-2B match |
| October 2022 | 3-year filing time limit introduced under Finance Act 2022 |
| November 2022 | 6-digit HSN codes made mandatory for AATO >₹5 Crore in Table 12 |
| October 2024 | Invoice Management System (IMS) goes live on GST portal |
| February 2025 | Mandatory HSN dropdown in Table 12; auto-populated descriptions; no manual HSN entry |
| May 2025 | Table 13 – Document series wise reporting becomes mandatory |
| July 2025 | GSTR-3B Table 3 hard-locked to GSTR-1 data; manual editing disabled; 3-year lock enforcement begins on portal |
| February 2026 | MRP-based GST reporting for tobacco goods in GSTR-1 |
| April 2026 | Fresh document series mandatory; LUT renewal; new GST rate structure (12% largely merged into 5%/18%); IMS fully enforced |
Pre-Filing Checklist for GSTR-1 FY 2026-27
Use this checklist every month (or quarter) before hitting the Submit button on your GSTR-1:
- Fresh Invoice Series: Confirm your billing software is using a new FY 2026-27 invoice, debit note, and credit note series from April 1, 2026.
- LUT Filed: If you are an exporter or SEZ supplier, confirm that Form RFD-11 for FY 2026-27 is approved and active before raising the first export invoice.
- E-Invoice Reconciliation: Reconcile all IRN-generated invoices with auto-populated GSTR-1 data. Add manually any exempt categories. Remove cancelled IRNs.
- HSN Codes Verified: All goods and services use correct HSN/SAC codes. For AATO >₹5 Cr, ensure 6-digit HSN; for AATO ≤₹5 Cr, ensure 4-digit HSN. Use portal dropdown only.
- Table 12 Checked: HSN-wise totals in Table 12 must match the sum of all invoices in Tables 4, 5, 6, 7 for that rate and HSN.
- Table 13 Populated: Document series details (first and last number, cancelled count) entered for all document types.
- GSTIN of Buyers Verified: All B2B invoices carry the correct, active GSTIN of the buyer. An inactive or incorrect GSTIN will deny ITC to the buyer.
- Place of Supply Correct: Interstate vs intrastate classification is correct. Place of supply determines IGST vs CGST+SGST split. Errors here can cause ITC mismatches for buyers.
- IMS Supplier View Checked: Review which invoices from the previous month have been rejected or kept pending by buyers. Decide on GSTR-1A amendments if needed.
- Credit Notes Communicated: Inform buyers about credit notes reported this period. Follow up on any pending IMS actions from buyers on your credit notes.
- Nil Return if No Sales: If there are no outward supplies this period, file nil GSTR-1 (via SMS or portal) before the due date.
- No Old Returns Pending: Confirm that there are no unfiled GSTR-1 returns for periods approaching the 3-year lock deadline.
- Advance Receipts Reported (Table 11): If you received advance payments for services this month for which invoices have not yet been issued, report them in Table 11.
- Tobacco Goods – MRP Method: If applicable, ensure taxable value is reported as net sale value and tax is manually entered based on MRP formula.
- GTA Reverse Charge Check: If you receive services from a Goods Transport Agency, confirm they have filed a written declaration for FY 2026-27 regarding their forward charge option. Report RCM supplies accurately.
Frequently Asked Questions (FAQs) on GSTR-1 FY 2026-27
What is the due date for filing GSTR-1 for monthly taxpayers in FY 2026-27?
Monthly GSTR-1 is due on the 11th of the following month for taxpayers whose aggregate annual turnover exceeded ₹5 crore in FY 2025-26. For example, April 2026 GSTR-1 is due on May 11, 2026. If the 11th falls on a public holiday, fiing is permitted on the next working day, but only if officially notified by CBIC — do not assume an extension without verification.
Can I still file GSTR-1 for FY 2022-23 periods in FY 2026-27?
It depends on the specific month. Under the 3-year filing lock introduced by Finance Act 2022, GSTR-1 cannot be filed after three years from the due date of that period. For example, March 2023 GSTR-1 (due April 11, 2023) could only be filed until April 11, 2026. From April 12, 2026 onwards, this return is permanently locked. For periods like April 2023 (due May 11, 2023), the lock deadline is May 11, 2026. Check each month individually and act immediately if any returns are pending.
What is GSTR-1A and when should I file it?
GSTR-1A is a post-filing amendment form introduced via CGST Notification dated July 10, 2024. It allows you to correct errors in a filed GSTR-1 for the same tax period — but only before filing GSTR-3B for that period. It is useful for: (a) correcting a wrong GSTIN in a B2B invoice, (b) amending taxable value or tax amounts, (c) responding to a buyer's rejection of your invoice in IMS. Once GSTR-3B for that period is filed, GSTR-1A is no longer available — corrections must be made in the next period's GSTR-1 amendment tables.
What happens if my buyer rejects my invoice in IMS?
When a buyer rejects your invoice in IMS, the rejected invoice does not appear in their GSTR-2B, meaning they cannot claim ITC on it. From your side as the supplier, the tax liability remains unchanged for that invoice in GSTR-3B. You should investigate the reason for rejection, communicate with the buyer, and if the invoice details were wrong, amend using GSTR-1A (before GSTR-3B) or via the amendment table in the next GSTR-1. If the invoice was correctly issued and the buyer rejected it in error, ask them to accept it via IMS — they can change their action before GSTR-3B is filed.
Is it mandatory to use the HSN dropdown in Table 12 of GSTR-1?
Yes. From February 2025 return period onwards, Table 12 of GSTR-1 requires HSN codes to be entered via a portal dropdown only. You cannot manually type an HSN code. The portal auto-populates the HSN description based on your dropdown selection. If your HSN code is not found in the dropdown, it means either the code is incorrect, outdated, or does not match the official HSN master. You must correct the HSN code in your billing records before filing.
What is Table 13 in GSTR-1 and is it mandatory in FY 2026-27?
Table 13 was made mandatory from the May 2025 return period. It requires taxpayers to report a document-wise summary of all documents issued during the tax period — including invoices, credit notes, debit notes, and cancelled documents. For each document series, you must enter the first document number, last document number, and total count. This table helps the GST department verify invoice continuity and detect gaps in reporting. Yes, it is fully mandatory in FY 2026-27 for all GSTR-1 filers.
I forgot to file LUT for FY 2026-27 before April 1. What do I do?
If you have already raised export invoices without a valid FY 2026-27 LUT, you have two options. Option 1: File the LUT (Form RFD-11) immediately on the GST portal — it can be filed retroactively for invoices within the current financial year in some cases, though the exact treatment depends on the facts and CBIC's stance. Option 2 (if LUT cannot cover past invoices): Pay IGST on those export invoices and then apply for a refund using the regular export refund route. Note that from April 2026, the ₹1,000 minimum refund threshold has been removed, so even small amounts are refundable. Consult your GST practitioner for the most appropriate remedy.
Can I file a nil GSTR-1 if there were no sales during the month?
Yes, filing a nil GSTR-1 is mandatory even if there were no outward supplies during the tax period. You have two options: (a) Log in to the GST portal and file GSTR-1 with all tables as nil, or (b) use the SMS facility — type NIL (space) R1 (space) your GSTIN (space) the tax period in MM/YYYY format, and send to 14409. You will receive a six-digit OTP for confirmation. Non-filing of nil GSTR-1 attracts a late fee of ₹20 per day (₹10 CGST + ₹10 SGST), subject to a maximum of ₹500 per return.
What are the late fees for delayed GSTR-1 filing in FY 2026-27?
The late fee for GSTR-1 (where there is tax liability) is ₹50 per day — ₹25 per day under CGST and ₹25 per day under SGST/UTGST — subject to a maximum of ₹10,000 per return (₹5,000 under each act). For nil GSTR-1 returns (no outward supplies), the late fee is ₹20 per day — ₹10 under CGST and ₹10 under SGST — subject to a maximum of ₹500 per return. In addition to the late fee, delayed filing blocks your buyer's ITC from appearing in GSTR-2B until you file, which directly harms your business relationships.
What is the time limit for amending a GSTR-1 entry from a previous financial year?
Amendments to invoices from previous financial years can be made in the amendment tables (Table 9, 9B, 9C, 10) of GSTR-1. The maximum time limit for such amendments is November 30 of the next financial year or the date of filing GSTR-9 (annual return) for that year — whichever comes earlier. For example, an invoice from FY 2025-26 that was incorrectly reported can be amended via Table 9 up to November 30, 2026 (or before GSTR-9 for FY 2025-26 is filed). Beyond this deadline, no amendments are possible and the error must be reported and explained in GSTR-9 itself.
Do QRMP taxpayers need to use IFF, or can they just file the quarterly GSTR-1?
IFF (Invoice Furnishing Facility) is optional but strongly recommended for QRMP taxpayers. In months 1 and 2 of each quarter, you can upload B2B invoice details via IFF so your buyers can claim ITC in that month's GSTR-2B rather than waiting until the quarter-end. Without IFF, your buyers (who are monthly GSTR-3B filers) will not see your invoices in their GSTR-2B for months 1 and 2 of the quarter. This creates cash flow issues for them and can damage your supplier relationship. If you skip IFF for months 1 and 2, all the quarter's invoices will appear in the buyer's GSTR-2B only after you file the quarterly GSTR-1.
Is there a difference between GSTR-2A and GSTR-2B, and which one matters for ITC in FY 2026-27?
Yes, there is an important difference. GSTR-2A is a real-time, dynamic document — it gets updated whenever a supplier files GSTR-1 or makes amendments. It reflects all invoices reported by your suppliers at any given time. GSTR-2B is a static, auto-drafted statement generated on the 14th of every month — it shows only those invoices filed by suppliers up to the 13th of that month and is used for actual ITC claims in GSTR-3B. From January 2022 onwards, ITC can only be claimed to the extent it appears in GSTR-2B (after IMS actions). GSTR-2A is useful for reconciliation; GSTR-2B is what governs your legal ITC entitlement.
My business turnover just crossed ₹5 crore in FY 2025-26. What changes in GSTR-1 filing for FY 2026-27?
If your AATO crossed ₹5 crore in FY 2025-26, several significant changes apply from April 1, 2026: (a) You must switch from quarterly to monthly GSTR-1 filing (due 11th of the following month). (b) E-invoicing is now mandatory for you — every B2B invoice, debit note, and credit note must have an IRN from the IRP before being issued to the buyer. (c) In Table 12, you must report 6-digit HSN codes instead of 4-digit. Update your ERP and billing software on all three points before April 1, 2026.
Can I still file GSTR-1 after the due date? What is the penalty?
Yes, GSTR-1 can be filed after the due date — subject to the 3-year outer time limit discussed above. However, late filing attracts late fees (₹50/day for taxable returns; ₹20/day for nil returns, with respective caps). More importantly, your buyers' GSTR-2B will not be updated with your invoices until you file, denying them timely ITC. Also, from FY 2026-27, if your GSTR-3B (which depends on GSTR-1 data due to hard-locking) is affected by a late GSTR-1, interest at 18% per annum applies on any tax shortfall. The combined impact of late filing — fees, buyer impact, interest — makes timely filing essential.
What is the GST rate rationalization in FY 2026-27 and how does it affect GSTR-1?
From April 1, 2026, the GST rate structure has been rationalized. The 12% tax slab has been largely eliminated — most goods previously taxed at 12% have moved to either 5% (essential goods) or 18% (standard products). The simplified rate structure is now broadly 0%, 5%, 18%, and 28% (plus applicable cess for luxury/demerit goods). This directly affects GSTR-1 filing because you must ensure the correct updated rate is applied to every invoice and correctly reflected in Table 12 (HSN-wise summary). Update your billing software with the revised rates before raising the first invoice of April 2026.
Conclusion: Stay Ahead of GSTR-1 Compliance in FY 2026-27
GSTR-1 in FY 2026-27 is no longer just a monthly data upload exercise — it is the foundation on which your buyers' ITC, your own GSTR-3B liability, and the entire GST reconciliation ecosystem rests. With the hard-locking of GSTR-3B from GSTR-1 data, the IMS making every invoice a tracked two-party transaction, and the 3-year portal lock permanently closing filing windows for older periods, the cost of errors and delays has never been higher.
The most important actions for this financial year: start with a fresh invoice series from April 1, 2026, renew your LUT if you are an exporter, set up e-invoicing if you have just crossed ₹5 crore turnover, and make IMS monitoring a weekly routine rather than a monthly afterthought. The pre-filing checklist in this article can serve as your month-end control procedure.
Indian GST is moving swiftly toward a fully digital, real-time compliance environment. Businesses that invest in accurate records, timely filing, and updated software will find that GST compliance actually becomes smoother each year. The risk is entirely on the side of inaction and delay.
If you found this guide helpful, bookmark it as your GSTR-1 reference for the year and share it with your accounts team. For any specific queries on your situation — multi-GSTIN filing, branch-level e-invoicing, or IMS amendment scenarios — consult a qualified GST practitioner.