Submitting GSTR-1 in GST Portal

Submitting GSTR-1 in GST Portal: A Complete 2026 Guide

The short answer: GSTR-1 is the monthly or quarterly statement of outward supplies that every regular GST taxpayer must file under Section 37 of the CGST Act, 2017. For FY 2026-27, monthly filers must submit by the 11th of the following month; QRMP-quarterly filers by the 13th of the month after the quarter ends. Your GSTR-1 data flows directly into your buyers' GSTR-2B, so a delay or error on your side blocks their input tax credit (ITC) — making timely, accurate filing a shared commercial obligation, not just a compliance formality. With e-invoice auto-population, GSTR-1A in-period amendments, and IFF now embedded into the workflow, the GSTN portal has meaningfully reduced the manual effort. This guide walks you through each step.

Who Must File GSTR-1 — and on Which Schedule

Every regular GST-registered taxpayer must file GSTR-1. The following categories are specifically excluded:

• Composition taxpayers (they file GSTR-4 annually)
• Input Service Distributors (ISDs)
• Non-resident taxable persons (they file GSTR-5)
• OIDAR service providers (they file GSTR-5A)
• TDS deductors under Section 51 (they file GSTR-7)
• TCS collectors — e-commerce operators under Section 52 (they file GSTR-8)

If you are a regular taxpayer — manufacturing, trading, or service-providing — GSTR-1 applies regardless of whether you made any sales in the period. A zero-turnover period still requires a nil GSTR-1, which you can file by SMS from your registered mobile number using the format specified on the GSTN portal, without logging into the portal at all.

Monthly vs. Quarterly: Which Category Are You?

Aggregate turnover is defined under Section 2(6) of the CGST Act — it includes taxable, exempt, and zero-rated supplies and exports across all GSTINs on a single PAN, but excludes inward supplies attracting reverse charge. Compute it on a PAN-India basis, not per-GSTIN.

A critical point: GSTR-1 is a declaration return only. No tax is paid at this stage. Output tax liability is paid through GSTR-3B. However, GSTR-1 directly determines what ITC your buyers can claim and what your own tax liability reconciliation looks like in GSTR-3B — so errors here have downstream consequences in both directions.

What Has Changed in GSTN: Current Features for FY 2026-27

The GSTN portal has evolved significantly. These are the features that directly change how you file.

E-Invoice Auto-Population into GSTR-1

If your aggregate turnover exceeds the currently notified e-invoicing threshold (Rs. 5 crore as of the last notified reduction), every B2B invoice, credit note, or debit note generated on an IRP (Invoice Registration Portal) is automatically pushed to Table 4 (B2B supplies) and the related CDN tables in your GSTR-1. You do not re-key these invoices.

What this means in practice:

• For high-volume B2B sellers, the bulk of Table 4 arrives pre-filled.
• You must still review each pre-populated record. Errors made at the IRP stage — wrong buyer GSTIN, wrong supply type, wrong taxable value — carry into GSTR-1 exactly as entered. The portal does not self-correct.
• If you spot a GSTIN error, cancel the IRN within the cancellation window (currently 24 hours from generation on most IRPs) and generate a fresh IRN before the GSTR-1 due date.
• B2C supplies, exports (Tables 6A/6B), and nil-rated supplies (Table 8) are not auto-populated from IRP and must be entered manually in every period.

GSTR-1A: In-Period Amendment Before GSTR-3B

GSTR-1A is a relatively new facility introduced under Section 37A of the CGST Act (inserted by the Finance Act 2024). It is the most practical quality-control tool available to a regular filer.

Here is the sequence:

1. You file GSTR-1 on the 11th (or 13th for quarterly).
2. A buyer contacts you: one of your invoices has the wrong taxable value, or the GSTIN was entered incorrectly.
3. Before you file GSTR-3B for that same period, you open GSTR-1A on the portal, correct the specific records, and file.
4. GSTR-1A updates the buyer's GSTR-2B so they receive the corrected ITC figure — without you carrying the amendment into the following month's Table 9.

Critical limitation: GSTR-1A can be filed only once per tax period. Once you file GSTR-3B for that period, the GSTR-1A window is permanently locked. Amendments after that point must use the amendment tables (Tables 9, 10, 11) in a subsequent GSTR-1, and the ITC correction will only reach the buyer in the following period's GSTR-2B.

Use GSTR-1A proactively. If you are a high-volume B2B supplier, build a 24-hour review window between GSTR-1 submission and GSTR-3B filing.

IFF (Invoice Furnishing Facility) for QRMP Taxpayers

QRMP-quarterly filers submit GSTR-1 once a quarter, but their B2B buyers — many of whom are monthly filers — need ITC reflected every month. IFF bridges this gap by allowing QRMP taxpayers to upload B2B invoice details for Month 1 and Month 2 of each quarter. These invoices then appear in the monthly buyer's GSTR-2B for that specific month, rather than being bunched into the quarterly GSTR-1.

IFF is optional, not mandatory. But if you are a QRMP taxpayer servicing large corporate buyers, skipping IFF for Months 1 and 2 delays their ITC by up to three months — a significant working-capital impact that can strain the business relationship.

Enhanced Validation and Live Tax-Liability Summary

The portal now runs real-time validation as you build your GSTR-1:

• HSN code format check against the live HSN master
• Place-of-supply consistency with supplier and buyer GSTINs
• Rate cross-check against the commodity or service description
• A running total of tax liability by head — IGST, CGST, SGST, Cess — that updates as you add invoices

This live summary is your pre-submission reconciliation tool. Compare it against your GSTR-3B draft before you file either return.

Understanding the Key Tables Inside GSTR-1

GSTR-1 has 13 tables. You fill only those applicable to your supply types in a given period.

Step-by-Step: How to Submit GSTR-1 on the GST Portal

Here is the exact sequence on the GST portal (www.gst.gov.in) as it stands today.

Step 1 — Log in and open Returns Dashboard Navigate to Services → Returns → Returns Dashboard. Select Financial Year 2026-27 and the relevant return filing period (e.g., April 2026 for monthly, or Apr–Jun 2026 for quarterly). Click Search. The GSTR-1 tile appears. Choose Prepare Online for direct entry, or Prepare Offline if you are uploading a JSON file from Tally, Zoho Books, or another ERP.

Step 2 — Review auto-populated e-invoice data If you are above the e-invoicing threshold, Table 4 will carry pre-populated records from the IRP. For each record, verify:

• Buyer's GSTIN matches your invoice
• Taxable value and tax amounts match your books (the IRP uses the invoice value you entered — any rounding differences will carry over)
• Supply type is correctly classified (B2B, exports, reverse charge)

Do not delete and re-enter auto-populated invoices unless unavoidable. The original IRN remains linked to the portal record.

Step 3 — Add supplies not covered by e-invoice auto-population Manually enter or upload:

• B2C large invoices (Table 5) — each individual invoice to an unregistered out-of-state buyer exceeding Rs. 2.5 lakh
• B2C small summary (Table 7) — consolidated by state and tax rate
• Exports (Table 6A if IGST paid, Table 6B if under LUT/bond) — include shipping bill numbers and port codes
• Credit notes and debit notes for the period, both to registered (Table 9B) and unregistered buyers (Table 10)
• Nil-rated, exempt, and non-GST supplies (Table 8) — report consolidated figures for the period

Reverse-charge inward supplies are not reported in GSTR-1. They go into GSTR-3B Table 3.1(d). A common error is trying to enter RCM liability here — it simply does not belong in this return.

Step 4 — Complete the HSN summary (Table 12) For FY 2026-27, the HSN digit requirements are:

• Aggregate turnover above Rs. 5 crore → 6-digit HSN mandatory for all supplies
• Aggregate turnover up to Rs. 5 crore → 4-digit HSN required for B2B; 4-digit recommended for B2C
• Aggregate turnover below Rs. 1.5 crore → 2-digit chapter code acceptable for B2C, but maintain 4-digit for B2B as best practice

The portal auto-generates the HSN summary from invoice data already entered. Your job is to review it, correct any HSN mismatches, and ensure the UQC (Unit Quantity Code) and quantity are correct.

Step 5 — Complete the Document Summary (Table 13) Enter the starting and ending invoice numbers for each document series you used in the period — tax invoices, revised invoices, debit notes, credit notes, advance receipt vouchers. This table is not optional. Leaving it blank is one of the triggers for a system-generated scrutiny notice under Section 61.

Step 6 — Preview, validate, and reconcile Click Preview Draft GSTR-1 to download a summary PDF. Check:

• Total taxable value and tax per head against your books
• IGST vs. CGST/SGST split — confirm the place of supply is correct for each transaction
• HSN summary total reconciles with the net taxable value
• Fix all validation errors before proceeding

Step 7 — Submit, then file Click Submit — this freezes the GSTR-1. Post-submit corrections require GSTR-1A (before GSTR-3B) or amendment tables in a future GSTR-1 (after GSTR-3B). Then click File GSTR-1 and authenticate:

• DSC (Digital Signature Certificate) — mandatory for companies and LLPs
• EVC (Electronic Verification Code to registered mobile/email) — for individuals and proprietorships
• Aadhaar OTP — if Aadhaar is linked and authenticated on the GST portal

You receive an ARN (Acknowledgement Reference Number). Save it. Your buyers' GSTR-2B for the period will reflect your invoices once GSTR-2B is generated on the 14th of the following month.

IFF Filing: Step-by-Step for QRMP Months 1 and 2

If you are on the QRMP scheme, the IFF flow mirrors GSTR-1 but with a narrower scope:

1. Go to Returns Dashboard → select Month 1 or Month 2 of the quarter
2. The IFF tile appears — click Prepare Online
3. Enter only B2B invoices and B2B credit/debit notes — IFF does not accept B2C, export, nil-rated, or HSN summary data
4. Validate, submit, and file before the 13th of the following month
5. The IFF data auto-carries into the quarterly GSTR-1 — do not re-enter it in the quarterly return

Worked Example: The Real Cost of a Late GSTR-1

Scenario: A Delhi-based B2B manufacturer (regular monthly filer, aggregate turnover Rs. 8 crore in FY 2025-26) fails to file GSTR-1 for April 2026. The due date was 11 May 2026. He files on 19 July 2026 — 69 days late.

Statutory late fee: Under Section 47 of the CGST Act, the late fee is Rs. 100 per day under CGST, subject to a cap of Rs. 5,000. The applicable SGST Act mirrors this. The GST portal computes the fee at filing and requires it to be paid before the return is accepted.

For 69 days of delay: Rs. 6,900 CGST + Rs. 6,900 SGST = Rs. 13,800 — but both caps apply, limiting the fee to Rs. 5,000 CGST + Rs. 5,000 SGST = Rs. 10,000 total. CBIC has issued periodic reduction notifications slabbed by turnover; check the portal for the applicable amount in your specific case.

The bigger cost — ITC blocked for your buyer: This manufacturer had issued B2B invoices to a Noida trading company: taxable value Rs. 15,00,000 at 18% IGST = Rs. 2,70,000 in ITC owed to that buyer for April 2026.

Because GSTR-1 was not filed, those invoices did not appear in the buyer's GSTR-2B for April. The buyer was forced to pay Rs. 2,70,000 from the cash ledger in their April GSTR-3B. That Rs. 2,70,000 sat blocked in the buyer's hands for 69 days, instead of being offset against output liability.

Approximate interest cost to the buyer on blocked funds: Rs. 2,70,000 × 18% per annum × (69 ÷ 365) = approximately Rs. 9,200

What the supplier actually faced:

• Rs. 10,000 in late fees — direct and quantifiable
• One significant buyer locked out of Rs. 2,70,000 ITC for over two months
• Risk of e-way bill generation being blocked if the lapse extended to two consecutive periods under Rule 138E of the CGST Rules
• A strained commercial relationship that no late fee can repair

The late fee is the accounting entry. The ITC disruption to your buyer is the real consequence.

Common Mistakes and How to Fix Them

Mistake 1: Accepting e-invoice pre-population without review Auto-populated data is only as accurate as what you sent to the IRP. A wrong buyer GSTIN entered at invoice generation will sit in Table 4 under the wrong recipient's record. The fix: before submitting GSTR-1, export Table 4 to Excel and cross-check buyer GSTINs against your sales ledger. Correct on the portal before you submit.

Mistake 2: Wrong place of supply, wrong tax head The first two digits of a GSTIN indicate the state code. If supplier and buyer are in the same state, apply CGST + SGST. If in different states, apply IGST. Getting this wrong means your buyer receives IGST credit when they need CGST/SGST (or vice versa), and the credit may not be fully offsettable against their output liability. This requires an amendment in the following period's GSTR-1 Table 9, delaying the correction by a full month.

Mistake 3: Omitting Table 8 for nil-rated and exempt supplies Businesses with a mix of taxable and exempt supplies — a food processor, a composite contractor, a hospital with both taxable and exempted services — frequently leave Table 8 blank. GST scrutiny officers cross-check Table 8 against the taxpayer's audited financials and the annual return GSTR-9. An unexplained gap draws a formal notice under Section 61. Fill Table 8 with the consolidated figures for nil-rated, exempt, and non-GST supplies every period.

Mistake 4: Mismatch between GSTR-1 tax liability and GSTR-3B The tax liability you declare in GSTR-1 is the system's reference point when you file GSTR-3B. If GSTR-1 shows Rs. 5,00,000 output IGST but GSTR-3B reflects Rs. 4,50,000, the portal auto-generates a discrepancy notice. Reconcile the two returns before filing GSTR-3B. The live tax-liability summary on the GSTR-1 preview screen exists precisely for this purpose.

Mistake 5: Attempting GSTR-1A after GSTR-3B is filed The portal closes GSTR-1A permanently once GSTR-3B for that period is filed. If you find an invoice error at that stage, the only path is the amendment tables in the next period's GSTR-1. Build a review step between GSTR-1 submission and GSTR-3B filing — even 24 hours of cross-checking against your accounts can catch errors while GSTR-1A is still available.

Mistake 6: Uploading JSON files without offline-tool validation Taxpayers uploading bulk JSON from accounting software often skip the GSTN Offline Tool validation step — and then face upload rejections because HSN codes are in 4-digit format when 6-digit is required, or the UQC is non-standard. Download the GSTN Offline Tool from the portal, validate your JSON locally, resolve all flagged errors, and then upload. This takes an extra 15 minutes and saves hours of troubleshooting.

Mistake 7: Skipping IFF as a QRMP taxpayer with monthly-filing buyers IFF is optional, but "optional" does not mean "without consequence." If your buyers file monthly and depend on your invoices for significant ITC, every month you skip IFF is a month they wait. Consider IFF as a relationship management tool, not just a compliance option. File it for Months 1 and 2 whenever your B2B invoice volume for the month is material.

Key Takeaways

• GSTR-1 due dates for FY 2026-27: 11th of the following month for monthly filers; 13th of the month following the quarter-end for QRMP filers; IFF by the 13th of each of the first two months of every quarter.
• E-invoice auto-population reduces data entry but does not replace review — buyer GSTIN errors and supply-type misclassifications from the IRP carry into GSTR-1 unchanged.
• GSTR-1A is your in-period error-correction tool — it works only before GSTR-3B is filed for the same period. After that, the window closes permanently.
• A delayed GSTR-1 harms your buyers as much as it harms you — ITC is blocked, the buyer's working capital is tied up, and repeated delays under Rule 138E trigger e-way bill restrictions on your outward movement of goods.
• Late fees are capped but not zero — Section 47 of the CGST Act imposes fees up to Rs. 10,000 per return under CGST + SGST combined; CBIC reduction notifications may apply, but the portal collects the applicable fee before accepting your return.
• Table 12 (HSN summary) and Table 13 (document summary) are not optional — both are scrutiny triggers when left blank; 6-digit HSN is mandatory for taxpayers above the Rs. 5 crore turnover threshold.
• Reconcile GSTR-1 output tax with your books and your GSTR-3B draft before filing either return — the live tax-liability summary in the portal preview screen makes this a five-minute step, not a full-day exercise.

All procedures and references reflect the CGST Act, 2017, IGST Act, 2017, and CGST Rules, 2017 as applicable for FY 2026-27. Verify current notifications and portal updates at www.gst.gov.in before relying on any specific rate or due date.