Filing GSTR One in India: Outward Supplies Return Walkthrough

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 to auto-fill the liability in your own GSTR-3B. If your GSTR-1 is inaccurate or late, your customers cannot see the ITC, and your own GSTR-3B liability will be wrong.

To file GSTR-1, you first log in to the GST portal with your username and password. See our GST login and GSTR-1 filing guide for the screens.

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 and Rule 59 of the CGST Rules.

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.

Deep-dive guide: If you are reporting B2B invoices, see GSTR-1 Tables 4A, 4B, 4C: Complete B2B Invoice Guide for mandatory fields, worked examples, and common errors.

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)
• Suppliers of online information and database access services from outside India (they file GSTR-5A)
• 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 (Section 39(10)).

GSTR-1 Due Dates for FY 2026-27

Deadline Timeline

GSTR-1 Key Due Dates: FY 2026-27

Monthly filers: 11th of the following month. Quarterly QRMP filers: 13th of the month after the quarter ends.

1. 11 May 2026

   Monthly: April 2026

   Monthly filers (mandatory above Rs 5 crore AATO); file by the 11th each month

2. 13 July 2026

   Quarterly Q1: Apr to Jun 2026

   QRMP scheme; AATO up to Rs 5 crore

3. 13 October 2026

   Quarterly Q2: Jul to Sep 2026

   QRMP scheme; IFF window 1st to 13th after each of the first two months

4. 13 January 2027

   Quarterly Q3: Oct to Dec 2026

   QRMP scheme; IFF capped at Rs 50 lakh of invoices per month

5. 11 April 2027

   Monthly: March 2027

   Last monthly filing of FY 2026-27

6. 13 April 2027

   Quarterly Q4: Jan to Mar 2027

   QRMP scheme; last quarterly filing of FY 2026-27

Source: Section 37 CGST Act; Rule 59 CGST Rules; Notification 83/2020-Central Tax

Monthly Filers

Businesses with aggregate annual turnover exceeding Rs 5 crore in the preceding financial year must file GSTR-1 every month. Smaller businesses that do not opt for QRMP also file monthly. 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 (Section 37(4)). 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 month (monthly filer) or the preceding quarter (quarterly filer), the portal blocks your GSTR-1 filing (Rule 59(6)).

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 bar is in Section 37(5) of the CGST Act, inserted by the Finance Act, 2023 and in force from 1 October 2023 (Notification 28/2023-Central Tax). GSTN enforced it on the portal from the July 2025 tax period. The same bar applies to GSTR-3B (Section 39(11)) and GSTR-9 (Section 44(2)). As of September 2026, returns for periods up to mid-2023 are already barred, so file any pending returns oldest first.

Understanding the GSTR-1 Tables

GSTR-1 has Tables 1 to 3 for basic details and reporting Tables 4 to 15. 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 that collect TCS

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 Large (Inter-State Supplies to Unregistered Persons)

Table 5 (B2C Large) covers inter-state supplies to unregistered persons where the invoice value exceeds Rs 1 lakh. These are reported invoice by invoice with the place of supply. The limit was cut from Rs 2.5 lakh to Rs 1 lakh with effect from 1 August 2024 (Rule 59(4), amended by Notification 12/2024-Central Tax dated 10 July 2024). Table 5A covers your own supplies and Table 5B supplies made through an e-commerce operator.

All other B2C supplies (intra-state of any value, and inter-state up to Rs 1 lakh) go to Table 7 (B2C Others), reported in consolidated form by place of supply and rate.

Table 6A: Exports

All exports of goods and services. 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.

Tables 6B and 6C: SEZ Supplies and Deemed Exports

• Table 6B: Supplies to SEZ units and SEZ developers, with or without payment of IGST
• Table 6C: Deemed exports

Table 7: B2C Others

Consolidated B2C supplies not covered in Table 5, by place of supply and rate.

Table 8: 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 9: Amendments and Credit/Debit Notes

• Table 9A: Amendments to B2B, B2C Large and export invoices reported in earlier periods (including correcting the recipient GSTIN)
• Table 9B: Credit and debit notes issued, to registered persons and (for B2C Large and exports) to unregistered persons
• Table 9C: Amendments to credit and debit notes reported in earlier periods

Table 10: Amendments to B2C Others

Corrections to consolidated B2C Others (Table 7) figures reported in earlier periods.

Table 11: Advances Received and Adjusted

• Table 11A: Advances received for which invoices have not yet been issued (for services, tax is payable on advances)
• Table 11B: Adjustment of advances against invoices issued in the current period
• Table 11(II): Amendments to advance details of earlier 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

Under Phase-III of HSN reporting (GSTN advisories of January 2025), HSN codes must be selected from a dropdown menu on the portal instead of being typed in, and the summary is split into B2B and B2C tabs.

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, total count and cancelled documents are declared.

Tables 14 and 15: E-Commerce Supplies

• Table 14: Supplies made through e-commerce operators, both those on which the operator collects TCS under Section 52 and those on which the operator pays tax under Section 9(5)
• Table 15: Supplies notified under Section 9(5), reported by the e-commerce operator

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, available from the August 2024 tax period, 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 the July 2025 tax period, the liability auto-populated in Table 3 of GSTR-3B from GSTR-1, GSTR-1A and IFF is non-editable (GSTN advisory dated 7 June 2025). If you spot an error in your outward supply figures, fix it through GSTR-1A before filing GSTR-3B, or in a later period's GSTR-1. This makes GSTR-1A more important than it was before.

E-Invoice Auto-Population

If your business is covered under e-invoicing (mandatory from 1 August 2023 where aggregate turnover in any financial year from 2017-18 exceeds Rs 5 crore, Notification 10/2023-Central Tax), your e-invoice data is automatically populated into GSTR-1 by the GST portal. If your AATO is Rs 10 crore or more, invoices must be reported on the IRP within 30 days of the invoice date from 1 April 2025.

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
• 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

The late fee under Section 47 runs from the day after the due date until the date of filing:

Turnover-Based Caps on Late Fees

The maximum late fee per return is capped by Notification 20/2021-Central Tax:

Example: A business with AATO of Rs 3 crore files its August 2026 GSTR-1 (due 11 September 2026) on 21 September 2026, 10 days late. Late fee = 10 x Rs 50 = Rs 500, well under the Rs 5,000 cap.

Interest

Late filing of GSTR-1 itself does not attract interest because GSTR-1 does not involve tax payment. Interest arises in GSTR-3B: 18% per annum on tax paid late in cash (Section 50(1)), and 18% per annum on ITC wrongly availed and utilised (Section 50(3), read with Notification 13/2017-Central Tax as amended).

Step-by-Step Filing Process on the GST Portal

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

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 Large invoices in Table 5 and B2C Others in Table 7
• Report exports, SEZ supplies and deemed exports in Tables 6A to 6C
• Fill nil-rated, exempt and non-GST supplies in Table 8
• Enter credit/debit notes and amendments in Tables 9 and 10, and advances in Table 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 to 14409 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 5. 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 can fail or show warnings. Maintain an updated HSN master in your billing system.

File GSTR-1 before GSTR-3B. The portal does not allow GSTR-3B for a period until GSTR-1 for that period is filed (Section 39(10)). Once GSTR-3B is filed, errors in that period's GSTR-1 can be fixed only through amendments in a later GSTR-1.

Use GSTR-1A for last-minute corrections. If you discover an error after filing GSTR-1 but before GSTR-3B, file GSTR-1A. From the July 2025 tax period, this is the only way to change that period's liability, because the auto-populated liability in GSTR-3B Table 3 is hard-locked.

Related Reading

For the return where you pay tax and claim ITC based on your GSTR-1 data, see the GSTR-3B filing guide. Tax Garden's GST return filing service can prepare and file both GSTR-1 and GSTR-3B for you. 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. For a complete GST compliance roadmap covering registration, all return due dates, ITC rules, and penalties, see The Ultimate GST Compliance Checklist for New Businesses.

Sources consulted: Section 37 and Section 47 of the CGST Act and Rule 59 of the CGST Rules (cbic-gst.gov.in); Notifications 20/2021, 28/2023 and 12/2024-Central Tax; GST portal user manuals and FAQs on GSTR-1, GSTR-1A and IFF (tutorial.gst.gov.in); GSTN advisories on HSN reporting, the GSTR-3B liability lock and the three-year filing bar.

Frequently Asked Questions

Do I need to file GSTR-1 if I made no sales in the month?

Yes. A registered regular taxpayer must file GSTR-1 for every period, including a nil return when there are no outward supplies. A nil GSTR-1 can be filed on the portal or by SMS from the authorised signatory's registered mobile. Skipping it attracts a late fee and blocks later returns.

When must a B2C invoice be reported separately in GSTR-1?

An inter-state invoice to an unregistered buyer above Rs 1 lakh, reduced from Rs 2.5 lakh from August 2024, must be reported invoice by invoice in Table 5 as B2C large, with the place of supply. All other B2C sales, intra-state or smaller inter-state ones, are reported in consolidated form by rate and state.

How many HSN digits must I report in the GSTR-1 HSN summary?

If aggregate turnover in the previous year was up to Rs 5 crore, report at least 4-digit HSN codes for B2B supplies. Above Rs 5 crore, 6-digit codes are required. HSN codes are now picked from a dropdown on the portal and the summary is split into B2B and B2C tabs, so keep the HSN master in your billing software current.

What is GSTR-1A and when should I use it?

GSTR-1A lets you add missed invoices or correct details reported in GSTR-1 for a period after filing it but before filing GSTR-3B for the same period. It can be filed once per period, and it cannot be used to change the recipient's GSTIN. Since the outward supply figures that GSTR-1 feeds into GSTR-3B are auto-populated, GSTR-1A is the cleanest way to fix them before paying tax.

Can I file an old GSTR-1 that I missed several years ago?

Only within three years from its original due date. After that, the GST portal blocks filing of GSTR-1, GSTR-3B and other returns for that period, under the time-bar introduced by the Finance Act, 2023 and enforced on the portal from July 2025. If you have unfiled returns, file the oldest ones first before they cross that limit.