GSTR-1 Filing Guide: Outward Supplies Return India

How to File GSTR-1: The Complete Guide to Reporting Outward Supplies Under GST

GSTR-1 is the first return in the GST filing sequence. You report what you sold. The portal uses that data to populate your buyer's GSTR-2B and then auto-fill parts of your own GSTR-3B. If your GSTR-1 is inaccurate or late, your customers lose ITC visibility, and your own GSTR-3B numbers will not match.

This guide covers every table, every deadline, and every practical step a business owner or accountant needs to file GSTR-1 correctly in FY 2026-27.

What is GSTR-1?

GSTR-1 is a return of outward supplies. It captures every sale you made during the tax period, whether to a registered buyer (B2B), an unregistered consumer (B2C), an exporter, or an SEZ unit.

It is governed by Section 37 of the CGST Act (Section 44 under the Income Tax Act 2025 mapping is unrelated; the GST section remains 37).

Unlike GSTR-3B where you declare summary numbers and pay tax, GSTR-1 is purely about invoice-level and summary-level reporting of sales. No tax payment happens through GSTR-1.

Who Must File GSTR-1?

Every person registered under GST must file GSTR-1, with these exceptions:

• Composition scheme taxpayers (they file GSTR-4 instead)
• Input Service Distributors (they file GSTR-6)
• Non-resident taxable persons (they file GSTR-5)
• Taxpayers liable to deduct TDS under GST (they file GSTR-7)
• E-commerce operators collecting TCS (they file GSTR-8)

If you are a regular taxpayer, a casual taxable person, or an SEZ unit/developer, you must file GSTR-1.

Nil returns are mandatory. Even if you had zero sales in a month or quarter, you must file a nil GSTR-1. Skipping it triggers late fees and blocks your GSTR-3B filing.

GSTR-1 Due Dates for FY 2026-27

Monthly Filers

Businesses with aggregate annual turnover exceeding Rs 5 crore in the preceding financial year must file GSTR-1 every month. The due date is the 11th of the following month.

Quarterly Filers (QRMP Scheme)

Businesses with turnover up to Rs 5 crore can opt for the QRMP (Quarterly Return Monthly Payment) scheme. Under QRMP, GSTR-1 is filed quarterly, and the due date is the 13th of the month following the quarter.

Sequential Filing Rule

You cannot file GSTR-1 for the current period unless you have filed GSTR-1 for all preceding periods. If you skipped filing for a past month, the portal will not let you file the current one until you clear the backlog.

Similarly, if you have not filed GSTR-3B for the preceding two months (monthly filer) or the preceding quarter (quarterly filer), the portal blocks your GSTR-1 filing.

Three-Year Filing Cutoff

The GST portal permanently blocks GSTR-1 filing once three years have passed from the original due date of that return. This rule, under Section 37 of the CGST Act (effective from October 2023, enforced on the portal from July 2025), means you cannot go back and file very old returns. If you have any unfiled GSTR-1 from FY 2022-23 or earlier, check whether the window is still open.

Understanding the GSTR-1 Tables

GSTR-1 has 13 main reporting tables. Here is what each one captures.

Tables 4A, 4B, 4C: B2B Supplies to Registered Persons

These are the most important tables for businesses that sell to other GST-registered entities. You report invoice-level details: buyer GSTIN, invoice number, date, taxable value, and tax amounts (CGST, SGST, IGST, cess).

• Table 4A: Supplies to registered persons (other than reverse charge)
• Table 4B: Supplies attracting reverse charge at the recipient's end
• Table 4C: Supplies made through e-commerce operators

Every invoice you report here flows into your buyer's GSTR-2B. If you miss an invoice or enter the wrong GSTIN, your buyer cannot claim ITC on that purchase.

Table 5: B2C Supplies to Unregistered Persons

B2C supplies are split into two sub-tables based on interstate threshold:

• Table 5A (B2C Large): Interstate supplies to unregistered persons where the invoice value exceeds Rs 1 lakh. These are reported invoice-by-invoice with the Place of Supply (state). The threshold was reduced from Rs 2.5 lakh to Rs 1 lakh from August 2024 onwards.
• Table 5B (B2C Others): All other B2C supplies, both intra-state and interstate below the threshold. These are reported in consolidated form, grouped by rate.

Table 6A: Exports

All exports of goods and services, including supplies to SEZ units and SEZ developers, and deemed exports. You must mention whether the export is with payment of IGST or under Letter of Undertaking (LUT)/Bond without payment of tax. The shipping bill number and port code are required for goods exports.

Table 6B: Supplies to SEZ Unit/Developer

Separate reporting of supplies to SEZ entities, with or without IGST payment.

Table 7: Nil-Rated, Exempt, and Non-GST Supplies

All supplies that attract zero tax, whether nil-rated, exempt, or outside the scope of GST. Report these as consolidated values split between:

• Inter-state vs. intra-state
• To registered persons vs. unregistered persons

Table 8: Advances Received and Adjusted

• Table 8A: Advances received for which invoices have not yet been issued (tax is payable on advances for services)
• Table 8B: Adjustment of advances against invoices issued in the current period

Table 9: Amendments

• Table 9A: Amendments to B2B invoices reported in earlier periods (correcting GSTIN, taxable value, or tax amount)
• Table 9B: Credit and debit notes issued against B2B invoices
• Table 9C: Amendments to credit and debit notes reported in earlier periods

Table 10 and 11: Amendments to B2C and Export Data

Corrections to B2C Large invoices, export invoices, and advance adjustments reported in prior periods.

Table 12: HSN-Wise Summary

A summary of all outward supplies grouped by HSN code and tax rate, with quantity and taxable value. This table is split into two tabs: B2B and B2C.

HSN code digit requirements (based on preceding FY turnover):

• Turnover above Rs 5 crore: 6-digit HSN code mandatory
• Turnover up to Rs 5 crore: 4-digit HSN code mandatory for B2B supplies

From January 2025, HSN codes must be selected from a dropdown menu on the portal. Manual entry of HSN codes is no longer allowed.

Table 13: Documents Issued

A summary of all documents issued during the period: invoices, credit notes, debit notes, delivery challans, and receipt vouchers. The serial number ranges and total count must be declared. This helps the department track gaps in your invoice sequence.

Invoice Furnishing Facility (IFF) for QRMP Filers

Quarterly filers face a practical problem: their buyers have to wait until the quarter-end GSTR-1 is filed to see invoices in their GSTR-2B. The Invoice Furnishing Facility (IFF) solves this.

How IFF works:

• QRMP filers can upload B2B invoices for the first two months of each quarter through IFF
• The upload window is from the 1st to the 13th of the month following the relevant month
• The net value of invoices uploaded through IFF in a month is capped at Rs 50 lakh
• Invoices uploaded through IFF auto-populate into the quarterly GSTR-1, so you do not need to enter them again
• IFF is optional. If you do not use it, all your invoices simply go into the quarterly GSTR-1

What can be uploaded through IFF:

• B2B invoice details (Tables 4A, 4B, 4C, 6B, 6C of GSTR-1)
• Credit and debit notes for B2B invoices (Table 9B)
• Amendments to B2B invoices and credit/debit notes (Tables 9A, 9C)

What cannot be uploaded through IFF: B2C supplies, exports, nil-rated supplies, advances, and HSN summary. These go only in the quarterly GSTR-1.

GSTR-1A: Amending GSTR-1 Before Filing GSTR-3B

GSTR-1A is an optional facility to correct or add records in your GSTR-1 after filing GSTR-1 but before filing GSTR-3B for the same tax period.

When to use GSTR-1A:

• You filed GSTR-1 but realized you missed some invoices
• You need to correct taxable value or tax amounts in already-reported invoices
• Your buyer flags a mismatch and you need to fix it before GSTR-3B

Rules:

• GSTR-1A becomes available after GSTR-1 is filed (or after its due date, whichever is later)
• It can be filed only once per tax period
• Once GSTR-3B is filed for that period, GSTR-1A is no longer available
• You cannot change the recipient GSTIN through GSTR-1A. GSTIN corrections must go through amendments in a subsequent period's GSTR-1

From November 2025 onwards, the auto-populated values in Table 3.2 of GSTR-3B (derived from GSTR-1) are non-editable. If you spot an error in your outward supply figures, you must fix it through GSTR-1A before filing GSTR-3B. This makes GSTR-1A more important than it was before.

E-Invoice Auto-Population

If your business is covered under e-invoicing (currently mandatory for businesses with turnover above Rs 5 crore), your e-invoice data is automatically populated into GSTR-1 by the GST portal.

How it works:

• You generate invoices and upload them to the Invoice Registration Portal (IRP) to get an Invoice Reference Number (IRN)
• The GST portal pulls these e-invoice details from the IRP and populates them in your GSTR-1 within two business days
• The tax period in which the invoice appears is based on the document date, not the date you reported it on the IRP
• You can review, add non-e-invoice records (B2C, nil-rated), and file

E-invoice auto-population reduces manual data entry significantly, but you still need to verify the figures and add any transactions not covered by e-invoicing (B2C sales, exempt supplies, advances).

Late Fees and Penalties

Late Fee Structure

Turnover-Based Caps on Late Fees

Interest

Late filing of GSTR-1 itself does not attract interest because GSTR-1 does not involve tax payment. However, if the delay in GSTR-1 delays your GSTR-3B filing, interest at 18% per annum applies on the unpaid tax liability in GSTR-3B. If you claimed excess ITC or reduced output liability, the rate is 24% per annum.

Step-by-Step Filing Process on the GST Portal

Step 1: Log in. Visit gst.gov.in. Enter your GSTIN, username, and password.

Step 2: Navigate to GSTR-1. Go to Services > Returns > Returns Dashboard. Select the financial year and the return period (month or quarter). Click Search. The GSTR-1 tile will appear. Click Prepare Online (to enter data directly) or Prepare Offline (to upload a JSON file from accounting software).

Step 3: Enter or verify invoice data.

• If e-invoicing applies to you, check the auto-populated B2B data first
• Add any missing B2B invoices in Tables 4A/4B/4C
• Enter B2C sales in Table 5
• Report exports in Table 6A
• Fill nil-rated/exempt supplies in Table 7
• Enter advances in Table 8, amendments in Tables 9 through 11
• Complete the HSN summary in Table 12
• Enter document details in Table 13

Step 4: Generate summary. Click "Generate Summary" after all data is entered. Review the auto-computed tax liability figures.

Step 5: Preview. Use the Preview button to download a PDF of the entire return. Review it against your books.

Step 6: File. Click "Proceed to File." Select your signing method:

• EVC (Electronic Verification Code): An OTP is sent to the registered mobile number and email of the authorized signatory. Available for proprietorships, partnerships, and other non-corporate entities.
• DSC (Digital Signature Certificate): Mandatory for companies (private and public), LLPs, and foreign LLPs. The DSC must be registered on the GST portal.

After verification, the return is filed and an ARN (Acknowledgment Reference Number) is generated. Save this for your records.

Nil GSTR-1 Filing via SMS

If you have zero outward supplies for the period, you can file a nil GSTR-1 through SMS without logging into the portal.

Send an SMS in the prescribed format from the registered mobile number of the authorized signatory. The portal responds with a verification code. Reply with the code to confirm filing.

Practical Tips for Accurate GSTR-1 Filing

Reconcile invoices before filing. Cross-check your accounting software's sales register with the data you plan to report. Mismatches between your books and GSTR-1 create problems during annual return (GSTR-9) reconciliation.

Do not delay B2B invoice uploads. Your buyer's ITC depends on seeing your invoice in their GSTR-2B. Late or missing uploads directly hurt your business relationships. QRMP filers should use IFF monthly rather than waiting for the quarterly GSTR-1.

Watch the B2C Large threshold. Since August 2024, any interstate B2C invoice above Rs 1 lakh must be reported invoice-by-invoice in Table 5A. If you miss this and report it in consolidated B2C, the data does not match the portal's validation checks.

Get HSN codes right. The portal now enforces HSN codes through a dropdown. If your accounting software exports incorrect or outdated HSN codes, the upload will fail. Maintain an updated HSN master in your billing system.

File GSTR-1 before GSTR-3B. GSTR-1 must be filed before GSTR-3B for the same period (sequential filing rule). If you file GSTR-3B first by mistake, you cannot go back and fix GSTR-1 data for that period except through amendments in the next period.

Use GSTR-1A for last-minute corrections. If you discover an error after filing GSTR-1 but before GSTR-3B, file GSTR-1A. From November 2025, this is the only way to fix outward supply figures since GSTR-3B Table 3.2 is now hard-locked to GSTR-1 data.

Frequently Asked Questions

What is the due date for filing GSTR-1?

Monthly filers must file by the 11th of the following month. Quarterly filers under the QRMP scheme must file by the 13th of the month following the quarter. For example, the April 2026 monthly GSTR-1 is due by May 11, 2026.

Can I file GSTR-1 if I have not filed GSTR-3B for previous months?

No. If you have not filed GSTR-3B for the preceding two months (monthly filer) or the preceding quarter (quarterly filer), the GST portal blocks your GSTR-1 filing until the backlog is cleared.

What is the Invoice Furnishing Facility (IFF)?

IFF allows QRMP quarterly filers to upload B2B invoices monthly (for the first two months of each quarter) so their buyers can claim ITC without waiting for the quarterly GSTR-1. The upload window is from the 1st to 13th of the following month, capped at Rs 50 lakh net value per month.

Is HSN code mandatory in GSTR-1?

Yes. Businesses with turnover above Rs 5 crore must report 6-digit HSN codes. Those with turnover up to Rs 5 crore must report 4-digit HSN codes for B2B supplies. HSN codes must be selected from a dropdown on the portal since January 2025.

Can I revise GSTR-1 after filing?

GSTR-1 cannot be revised directly. However, you can use GSTR-1A to make corrections before filing GSTR-3B for the same period. After GSTR-3B is filed, corrections must be made through amendments in the next period's GSTR-1 (Tables 9, 10, 11).

What is the late fee for not filing GSTR-1 on time?

Rs 50 per day (Rs 25 CGST + Rs 25 SGST) for regular returns, and Rs 20 per day (Rs 10 + Rs 10) for nil returns. Late fees are capped based on your annual aggregate turnover.

What happens if I do not file GSTR-1 at all?

Your buyers cannot see your invoices in their GSTR-2B and lose ITC. Your own GSTR-3B filing gets blocked. Late fees accumulate daily. After three years from the due date, the portal permanently blocks filing for that period.

Related Reading

For the return where you pay tax and claim ITC based on your GSTR-1 data, see the GSTR-3B filing guide. For the annual return that reconciles your monthly or quarterly filings, see the GSTR-9 annual return guide. For details on GST late fees and interest across all return types, see the GST late fee and interest penalty guide.

Sources consulted: GST Portal (gst.gov.in) GSTR-1 FAQs and filing manual; CBIC notifications on HSN reporting and time-bar restrictions; ClearTax GSTR-1 guide; Tax2win GSTR-1 reference.