How to Log In and File GSTR-1 Step by Step in 2026

Quick Overview

GSTR-1 is the statement of outward supplies. It is the first return in the monthly GST cycle: every invoice, debit note and credit note you issue is reported here. Your B2B invoices flow into your buyer's GSTR-2A and GSTR-2B, and your GSTR-1 auto-populates the liability in your own GSTR-3B, so accuracy matters.

Filing Deadlines 2026:

• Monthly Filers: 11th of the next month
• Quarterly Filers (QRMP, aggregate turnover up to Rs 5 crore): 13th of the month after the quarter; optional IFF for B2B invoices of the first two months by the 13th of the next month

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Step 1: GST Portal Login

Before You Start

Have ready:

• Your portal username (created at registration) and password
• Access to the mobile number and email of the authorised signatory registered on the portal, for OTPs
• Your 15-digit GSTIN for reference

How to Log In to the GST Portal

1. Visit the GST Portal

   • Go to www.gst.gov.in
   • Click "Login" in the top-right corner

2. Enter Your Credentials

   • Username and Password
   • Type the captcha shown on screen

3. OTP Verification

   • If the portal asks for it, enter the OTP sent to the registered mobile number or email

4. Dashboard Access

   • Once logged in, you see your dashboard with a "Return Dashboard" button

Forgot Your Password?

1. On the login page, click "Forgot Password"
2. Enter your username and the captcha
3. Enter the OTPs sent to the registered mobile number and email
4. Set a new password: 8 to 15 characters with at least one uppercase letter, one lowercase letter, one number and one special character
5. Log in with the new password

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Step 2: Open GSTR-1

Once logged in:

1. Go to Services > Returns > Returns Dashboard
2. Select the Financial Year (for example 2026-27) and the Return Filing Period (the month, or the quarter for QRMP filers), then click Search
3. In the GSTR-1 tile, click "Prepare Online" or "Prepare Offline"

Tip: With many invoices, use the offline tool (Step 7) and upload in bulk. With a handful of invoices, fill directly online.

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Step 3: Understanding GSTR-1 Tables

GSTR-1 has tables numbered up to 15. Not all apply to your business:

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Step 4: How to Fill a B2B Invoice (Table 4A)

Example Calculation (18% GST)

Scenario: You provide IT consulting to a registered business:

• Taxable Value: Rs 10,000
• SAC: 998313 (IT consulting and support services)
• Supplier and buyer both in Telangana (intra-State)
• GST Rate: 18%

How to Fill:

• Buyer GSTIN, invoice number and invoice date
• Place of supply: 36-Telangana
• Taxable Value: Rs 10,000
• CGST: Rs 900 (10,000 x 9%)
• SGST: Rs 900 (10,000 x 9%)
• IGST: Rs 0 (not applicable for intra-State)
• Invoice Value: Rs 11,800 (10,000 + 1,800), which is the total amount on the invoice including tax

What If the Buyer Does Not Have a GSTIN?

A buyer without a GSTIN is unregistered. The sale is a B2C supply and goes in Table 5 or Table 7 (see the B2C tab above), not in Table 4A. The buyer cannot claim ITC on it.

Tip: Always ask for the GSTIN before invoicing, and verify it with "Search Taxpayer" on the GST portal. If a registered buyer gives you the GSTIN only after you have filed, correct it through Table 9A of a later GSTR-1.

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Step 5: HSN Code Selection

Why HSN Codes Matter

• Rate check: the HSN or SAC decides the GST rate, so a wrong code can mean the wrong rate and a tax demand
• Validation: from 2025 the portal requires HSN to be selected from a dropdown in Table 12, and checks the values against your invoice tables
• Reporting: the HSN summary must match the invoice-level data you report

How to Find Your HSN Code

1. Go to www.gst.gov.in
2. Open Services > User Services > Search HSN/SAC (no login needed)
3. Enter a product description or code (for example "trousers" or "software")
4. Note the code shown and check the current GST rate in the CBIC rate notifications for that code
5. Use the same code in Table 12 of GSTR-1

Tip: Fix your HSN or SAC codes once in your billing software and use them consistently on all invoices.

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Step 6: Table 12 (HSN Summary)

What is Table 12? A summary of all supplies by HSN or SAC code: quantity (for goods), taxable value and tax. From Phase III of HSN reporting (GSTN advisory of 22 January 2025, phased in over the early 2025 return periods), Table 12 has separate B2B and B2C tabs, and the HSN must be picked from a dropdown instead of typed.

Enter the HSN summary online or import it from your billing software or the offline tool (data from e-invoices, where applicable, is auto-populated). The portal checks it against the values in your other tables; these checks started in warning mode.

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Step 7: Upload and File Your GSTR-1

Option A: Online Filing (Few Invoices)

1. Fill each applicable table and click Save
2. Click "Generate Summary" and review the summary
3. Click "Preview" to check the draft
4. Click "File Statement" and verify with EVC (OTP to the authorised signatory) or DSC
5. The portal generates an ARN (acknowledgment reference number), sent by SMS and email

Companies must file with DSC. Other taxpayers can use EVC.

Option B: Offline Tool (Many Invoices)

1. Download the Returns Offline Tool from the Downloads section of www.gst.gov.in
2. Enter or import invoice data table by table (the tool accepts the GSTN Excel/CSV templates)
3. Validate the data in the tool and generate the JSON file
4. On the portal, in the GSTR-1 tile, click "Prepare Offline" > "Upload" and upload the JSON
5. If the upload has errors, download the error report, correct it in the tool and upload again
6. Then generate the summary and file as in Option A

Validation Checks Before Filing

• GST rates correct for each product or service
• HSN or SAC codes correct and at the required number of digits
• Invoice dates fall within the tax period, or are earlier invoices being reported now
• Buyer GSTINs valid (15 characters)
• Place of supply correct, so CGST+SGST and IGST are charged correctly
• Credit and debit notes linked to the original invoices

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Step 8: After Filing, What Happens Next?

Timeline

Deadline Timeline

After You File GSTR-1 (Monthly Filer)

Your filing feeds your buyers' credit and your own GSTR-3B

1. By 11th

   GSTR-1 Filed

   ARN generated and sent by SMS and email. Status on the Returns Dashboard changes to Filed.

2. On filing

   Buyers' GSTR-2A Updated

   Your B2B invoices appear in your buyers' GSTR-2A and their Invoice Management System (IMS), where they can accept, reject or keep them pending.

3. 14th

   Buyers' GSTR-2B Generated

   GSTR-2B for the month includes invoices filed up to the 11th cut-off. Buyers can claim ITC only on invoices shown in GSTR-2B (Section 16(2)(aa)).

4. Before GSTR-3B

   GSTR-1A Window

   GSTR-1A lets you add missed invoices or amend GSTR-1 of the same period, after GSTR-1 is filed and before GSTR-3B for that period is filed.

5. 20th

   GSTR-3B Deadline

   File GSTR-3B and pay net tax. Table 3 liability is auto-populated from GSTR-1 and GSTR-1A and cannot be edited from the July 2025 tax period.

Source: Sections 16, 37, 39 CGST Act; Rules 59, 60, 61 CGST Rules; GSTN Advisory 606 (7 June 2025)

If You Make a Mistake After Filing

• Before GSTR-3B is filed: use GSTR-1A to add or amend invoices of the same period
• After that: amend the invoice in Table 9A (or 9C, 10) of a later GSTR-1, or issue a credit or debit note
• Time limit: amendments and credit notes for a financial year are allowed until 30 November of the next year or the date of the annual return, whichever is earlier (Sections 34(2) and 37(3))
• A filed GSTR-1 cannot be revised or deleted; wrong invoices are corrected through amendments

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Checklist: Before You File GSTR-1

• All invoices issued in the period accounted for
• Buyer GSTINs verified (15 characters: 2-digit State code, 10-character PAN, entity number, the letter Z and a check digit)
• HSN or SAC codes selected for all products and services
• Tax rates verified against the current GST slabs (5%, 18% and 40% from 22 September 2025, plus special rates such as 3% on gold and 0.25% on rough diamonds; exports and SEZ supplies are zero-rated)
• Credit and debit notes linked to original invoices
• Export invoices with shipping bill details (if available)
• B2C Others summarised by State and rate; inter-State B2C invoices above Rs 1 lakh listed in Table 5
• No duplicate invoices
• Offline JSON validated before upload

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Next Steps

• Check the IMS and GSTR-2B (generated on the 14th) for your own purchase invoices before claiming ITC
• File GSTR-3B by the 20th (monthly filers) or the 22nd/24th after the quarter (QRMP filers)
• Pay the net tax by the GSTR-3B due date to avoid interest at 18% per year under Section 50(1)

Need help? Contact us via WhatsApp or email and we can help with your GSTR-1 filing. Our GST filing services cover GSTR-1 and GSTR-3B every month, including GSTR-2B reconciliation.