How to Log In and File GSTR One Step by Step in 2026

GST Login & GSTR One Filing Step-by-Step Guide 2026

Quick Overview

GSTR One is your outward supplies return. The first return in the GST filing cycle. Every invoice you issue goes here. Your buyer's GSTR TwoA is auto-populated from your GSTR One, so accuracy matters.

Filing Deadlines 2026:

• Monthly Filers: 11th of next month
• Quarterly Filers (QRMP): 13th of month after quarter ends

Estimated Reading Time: 25 minutes | Difficulty: Easy for freshers, routine for professionals

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Step 1: GST Portal Login - Complete Instructions

Before You Start

Have ready:

• Your 15-digit GSTIN (Goods and Services Tax Identification Number)
• Registered email address or User ID
• Your GST portal password
• 2FA mobile number linked to your GSTIN

How to Log In to GSTN Portal

Step-by-Step Guide

GST Portal Login: Step-by-Step

Have your GSTIN, password, and registered mobile ready before starting

1

Open GST Portal

Go to www.gst.gov.in in any browser. Click the Login button in the top-right corner of the homepage.

Start

2

Enter GSTIN

Type your 15-digit GSTIN in the first field. Format: 2-digit state code + 10-char PAN + 1-digit entity type + 1-digit check digit.

GSTIN

3

Enter User ID & Password

User ID is your registered email or custom username set during GST registration. Password is case-sensitive.

Credentials

4

Complete CAPTCHA

Enter the characters shown in the image. Click refresh if unclear.

Security

5

Click Login

Portal sends a 6-digit OTP to your registered mobile number for two-factor authentication.

Submit

Source: GSTN Portal: www.gst.gov.in

1. Visit the GST Portal

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

2. Enter Your Credentials

   • GSTIN/UIN: Enter your 15-digit GSTIN (the unique ID assigned after GST registration)
   • User ID: Enter your registered email address or custom User ID
   • Password: Enter your GST portal password

Step-by-Step Guide

GST Login Form: Field Reference

All fields are mandatory, any mismatch causes login failure

1

GSTIN / UIN

15-digit GST Identification Number assigned at registration. Starts with state code (e.g., 36 for Telangana). Do not confuse with PAN.

15 digits

2

User ID

The email address or custom User ID you created during GST registration. If forgotten, use Forgot Username on the login page.

Login ID

3

Password

Minimum 8 characters, case-sensitive. Must include a number and special character. Change every 180 days as the portal prompts.

Secure

4

CAPTCHA Code

5-character alphanumeric code shown on screen. Distinguishes uppercase O from zero, read carefully.

Anti-bot

Source: GST Portal login page: www.gst.gov.in/home

3. Two-Factor Authentication 2FA)
   • The portal sends an OTP (One-Time Password) to your registered mobile number
   • Enter the 6-digit OTP in the prompt box
   • Click "Submit" or "Verify"

Step-by-Step Guide

GST Portal 2FA: OTP Verification

OTP is valid for 10 minutes, enter it promptly

1

OTP Sent to Mobile

6-digit OTP is sent via SMS to the mobile number registered with GST. Check the number linked at time of GST registration.

SMS

2

Enter OTP

Type the 6-digit code in the verification box on screen. Do not include spaces.

Enter

3

Click Verify / Submit

Portal handles the OTP and opens your GST dashboard if correct.

Submit

4

OTP Not Received?

Wait 60 seconds, then click Resend OTP. If still not received, check if your registered mobile number is active and not on DND for transactional SMS.

Troubleshoot

Source: GSTN 2FA process: mandatory since April 2023

4. Dashboard Access
   • Once verified, you'll see your GST Dashboard
   • Look for "Services" or "File Return" menu on the left sidebar
   • Select "File GSTR One" to begin

Step-by-Step Guide

Navigate to GSTR One from GST Dashboard

After login, follow this exact path to reach the GSTR One filing screen

1

Click Services

In the left sidebar after login, click Services. A submenu expands.

Sidebar

2

Click Returns

Under Services, click Returns to see the returns submenu.

Menu

3

Click Returns Dashboard

Opens a screen where you select the filing period for any return.

Dashboard

4

Select Period

Choose Financial Year (e.g., 2026-27) and the month (e.g., June 2026). Click Search.

Period

5

Select GSTR One

In the results, find GSTR One row and click Prepare Online (for direct entry) or Prepare Offline (for bulk upload).

File

Source: GST Portal: Services > Returns > Returns Dashboard

Forgot Your Password?

1. On the login page, click "Forgot Password"
2. Enter your GSTIN or User ID
3. Verify via OTP sent to registered mobile
4. Create a new strong password (min 12 characters with numbers & symbols)
5. Click "Update Password" and log in with new credentials

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Step 2: Navigate to GSTR One Filing Section

Once logged in:

Step-by-Step Guide

GSTR One Navigation Path Summary

Exact click sequence from dashboard to filing

1

Dashboard

Starting point after successful login

Start

2

Services (Left Sidebar)

First click after login

Menu

3

Returns > Returns Dashboard

Second level navigation

Sub-menu

4

Select FY + Month + Search

Filter to your specific filing period

Filter

5

GSTR One Row > Prepare Online

Final click to open the GSTR One form

File

Source: GSTN Portal navigation

1. From dashboard, click "Services" (left sidebar)
2. Select "Returns" → "File GSTR One"
3. Choose Assessment Year (e.g., 2026-27 for FY 2025-26)
4. Click "Prepare Offline" or "File Now" depending on your data readiness

Pro Tip for Freshers: If you have many invoices, use "Prepare Offline" to fill in Excel, then upload bulk. For small businesses (< 50 invoices), fill directly online.

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Step 3: Understanding GSTR One Tables & Tabs

GSTR One has 13 tables. Not all apply to your business. Here's a quick guide:

Business Type & Applicable Tables

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Step 4: How to Fill GSTR One (Line-by-Line Instructions)

For B2B Invoices (Table 4A - Most Common)

Example Calculation 18% GST)

Scenario: You sold goods to another registered business:

• Invoice Value: Rs. 10,000
• HSN Code: 6204 (Garments)
• Within same state (Telangana)
• GST Rate: 18%

How to Fill:

• Invoice Amount: Rs. 10,000
• Taxable Amount: Rs. 10,000
• SGST: Rs. 900 10,000 × 9%)
• CGST: Rs. 900 10,000 × 9%)
• IGST: Rs. 0 (not applicable for intra-state)
• Total Tax: Rs. 1,800
• Final Invoice to Customer: Rs. 11,800 10,000 + 1,800)

What If Buyer Doesn't Have GSTIN?

Use Table 4B (B2B with missing GSTIN):

• Enter invoice details same as Table 4A
• GSTIN field: Leave blank or enter "UNREGISTERED"
• GST treatment: Same as Table 4A (you still charge GST)
• Risk: No ITC benefit for buyer; may attract GST notice

Step-by-Step Guide

GSTR One Table 4B: B2B Supply to Unregistered Buyer

Use Table 4B only when the buyer genuinely has no GSTIN, verify before using

1

Invoice Details

Fill Invoice Number, Date, and Value same as Table 4A. The only difference is that GSTIN is blank.

Same as 4A

2

GSTIN Field

Leave blank or enter URP (Unregistered Person). Do not enter any made-up GSTIN.

Leave Blank

3

Place of Supply

Enter the state code of the buyer's state. This determines IGST vs CGST+SGST even for unregistered buyers.

Mandatory

4

Tax Treatment

GST is charged and collected normally, same rates as Table 4A. The difference is only that the buyer cannot claim ITC.

No ITC for Buyer

5

Risk of using Table 4B

GST officers may query why a business buyer has no GSTIN. If buyer is actually registered, you face ITC denial + potential penalty. Always request GSTIN at point of sale.

Risk

Source: GSTR One Table 4B: B2B invoices for unregistered persons

Tip: Always request GSTIN from buyers. If they're registered and claim no GSTIN, flag it.

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Step 5: HSN Code Selection (Critical for Compliance)

Why HSN Codes Matter

✅ Affects your GST audit: Mismatched HSN codes trigger Department queries ✅ Determines ITC eligibility: Buyer needs matching HSN to claim ITC ✅ Tax rate verification: Wrong HSN = wrong tax rate = penalties

How to Find Your HSN Code

Method 1: Official GST Portal Search

1. Go to www.gst.gov.in
2. Click "Services" → "Search" → "Search HSN Code"
3. Enter your product description (e.g., "Ladies Trousers", "Software Development")
4. Portal returns 6-digit code, description, and applicable GST rates
5. Copy the code; use it in Table 12 (HSN Summary)

Method 2: Common HSN Codes by Business Type

Pro Tip: Document your HSN code once. Use it consistently across all invoices. If product changes, update HSN.

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Step 6: Table 12 - HSN Summary (Aggregate View)

What is Table 12? Sum of all HSN codes used across Tables 4A, 5B, 5C, etc. Portal auto-calculates this when you add line items.

Example for Multi-Product Business:

The portal auto-populates Table 12 from your individual entries. No manual action needed unless you spot errors.

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Step 7: Upload & File Your GSTR One

Option A: Direct Online Filing (Small Businesses)

1. Fill all tables directly in portal
2. Review each entry for accuracy
3. Click "Save" → "Submit"
4. Generate "Provisional ID" (PRN) - save this
5. Done - Filing complete within 2 minutes

Option B: Offline File Upload (Large Businesses)

For businesses with 100+ invoices:

1. Download "Excel Template" from portal
2. Fill invoice details in Excel (one row = one invoice)
   • Column A: Invoice No.
   • Column B: Invoice Date
   • Column C: GSTIN
   • ... (same columns as Table 4A)
3. Save as .csv or .xlsx
4. Go to portal → "Upload"
5. Select your file → "Validate"
6. Fix any errors shown in validation report
7. Re-upload corrected file
8. Click "Submit" once validation passes

Step-by-Step Guide

GSTR One Offline Excel Template: Column Reference

Download the template from portal. Do not use a custom Excel file

1

Column A: Invoice No.

Your invoice number. Max 16 alphanumeric characters. Must match the physical invoice exactly.

Text

2

Column B: Invoice Date

Date in DD-MM-YYYY format. Example: 15-06-2026. Do not use slashes in the offline template.

Date

3

Column C: Receiver GSTIN

15-digit GSTIN of buyer for Table 4A entries. Leave blank for Table 5B (B2C).

GSTIN

4

Columns D-F: Values

Invoice Value (total), Taxable Value (before GST), and GST Rate 5/18/40). All amounts in rupees, no paise.

Numbers

5

Columns G-J: Tax Amounts

IGST, CGST, SGST/UTGST, and CESS in separate columns. Enter only the applicable tax type, leave others as 0.

Tax

6

Column K: HSN Code

6-digit HSN/SAC code. Must be a valid code, portal handles against the HSN master list.

HSN

Source: GSTR One Offline Utility: download from GST Portal > Returns > Offline Tools

Step-by-Step Guide

Offline Excel Upload: Step-by-Step

Validate before submitting. Errors in the file will block filing

1

Save File Correctly

Save as .xlsx or .csv with UTF-8 encoding. File size must be under 2MB. Split into multiple files if over 2MB.

Prepare

2

Go to Upload Section

In GSTR One > Prepare Offline > Upload. Click Choose File and select your saved Excel.

Upload

3

Click Validate

System checks each row for format errors: invalid GSTIN format, date outside period, missing mandatory fields, invalid HSN.

Validate

4

Download Error Report

If validation fails, download the Error Report. It shows the exact row number and error description for each issue.

Fix Errors

5

Fix and Re-upload

Correct each error in your Excel file, save again, and upload. Repeat until validation passes with zero errors.

Iterate

6

Click Submit

Once validation passes with no errors, click Submit to file your GSTR One. Download the ARN confirmation.

Submit

Source: GSTR One Offline Utility instructions, GSTN

Validation Checks Before Submitting

✓ All GST rates correct for product/service
✓ HSN codes match your business type
✓ Invoice dates fall within the filing period 1st to last date of month)
✓ GSTIN format correct 15 digits, no spaces)
✓ Tax calculation correct (no manual math errors)
✓ Credit/Debit notes linked to original invoices

Pro Tip: If system shows "No errors", take a screenshot before submitting. File in portal always keeps a copy, but your backup helps with reference.

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Step 8: After Filing - What Happens Next?

Timeline

Deadline Timeline

Post-GSTR One Filing: What Happens Next

Your filing triggers a chain of events in the GST ecosystem

1. Day 0

   GSTR One Filed

   PRN generated. Status on dashboard changes to Filed. Acknowledgment sent to registered email.

2. Day 1-2

   System Validates Entries

   GSTN handles GSTIN formats, HSN codes, tax calculations. Errors appear in Messages section of dashboard.

3. Day 2-10

   Buyers' GSTR TwoA Updated

   All your B2B invoices appear in your buyers' GSTR TwoA. They can view and match against their purchase register.

4. By 13th

   GSTR OneA Amendment Window Open

   Use GSTR OneA to add omitted invoices or correct errors before GSTR ThreeB deadline.

5. 20th

   GSTR ThreeB Deadline

   File GSTR ThreeB and pay net GST due. Uses the outward supply data from your GSTR One.

Source: GST return filing cycle, CGST Rules 2017

If You Make a Mistake After Filing

✓ Can amend: Use "GSTR OneA" to add/modify invoices (file anytime before GSTR ThreeB deadline)
✗ Cannot change: Cannot delete already-filed invoices in original GSTR One

Step-by-Step Guide

GSTR OneA: How to Amend a Filed GSTR One

Available after GSTR One is filed; must be done before that month's GSTR ThreeB deadline

1

Navigate to GSTR OneA

Services > Returns > Returns Dashboard > Select the same period as your original GSTR One > Click GSTR OneA.

Navigate

2

Add Omitted Invoices

Click Add Invoice to add invoices you forgot to include in the original filing. Enter all fields same as Table 4A.

Omissions

3

Modify Existing Entries

Search for the original invoice by invoice number. Edit the fields you need to correct (value, GSTIN, HSN, tax amounts).

Corrections

4

Cannot Delete

You cannot remove an invoice already filed in GSTR One. For returns and cancellations, use a Credit Note in Table 7 instead.

Limitation

5

File GSTR OneA

After all corrections, click File. The amendments are reflected in your buyers' GSTR TwoA within 24 hours.

Submit

Source: GSTR OneA: Amendment to GSTR One, CGST Rule 59 5)

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Step 9: Common Mistakes & How to Avoid Them

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Checklist: Before You File GSTR One

• All invoices issued in the period accounted for
• Buyer GSTIN verified 15 digits, format: XX000XXXXXOXZ)
• HSN codes selected for all products/services
• Tax rates verified against current GST 2.0 slabs 5%, 18%, 40%; 0%, 0.25%, 3% for specific goods; 0% for zero-rated)
• Credit/Debit notes linked to original invoices
• Export invoices marked with Shipping Bill No. (if applicable)
• B2C sales aggregated by tax rate (not individual line items)
• No duplicate invoices listed
• Portal login working; password reset done if needed
• Offline file validated before upload (if uploading Excel)

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FAQ - GSTR One Filing

Q: Can I file GSTR One late?
A: Yes, but Rs. 50/day late fee applies (Rs. 25 CGST + Rs. 25 SGST) up to capped amount. File within 11 days of month-end to avoid.

Q: What if my buyer doesn't have GSTIN?
A: They're likely unregistered (turnover < Rs. 40 lakh). File in Table 4B. They can't claim ITC. Some states/businesses must register even below threshold. Flag for verification.

Q: How do I amend a filed GSTR One?
A: Use GSTR OneA (amendment form). Add missing invoices or correct amounts. File before month-end of next month.

Q: What's HSN code for services?
A: Services are 5-digit SAC codes, not HSN. Example: SAC 6202 for consulting. GST portal searchable under "SAC Code" tab.

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Next Steps

✅ Filed GSTR One? Now file GSTR Two (purchases) by month-end
✅ Reconcile with buyer's GSTR ThreeB
✅ File GSTR ThreeB by deadline 20th for monthly filers)
✅ Make GST payment on same day

Need help? Contact us via WhatsApp or email. We handle GSTR One filing for 500+ businesses monthly, checked for common errors before submission.