How to File GSTR-1 Online in 2026 — Complete Step-by-Step Guide for Small Businesses

GSTR-1 is a monthly (or quarterly) return that every GST-registered business must file. It reports all your outward supplies — every invoice you issued to customers, whether B2B or B2C. Missing or wrong GSTR-1 filings can block your customer's Input Tax Credit (ITC), damage your business relationships, and attract notices from the GST department.

This guide breaks it down simply, whether you are a shop owner, a trader, or a small service provider.

What is GSTR-1?

GSTR-1 is a statement of all sales you made during a month (or quarter). You declare:

• Every invoice raised to GST-registered buyers (B2B)
• Aggregate sales to non-registered buyers (B2C)
• HSN-wise summary of your goods/services
• Credit and debit notes
• Export invoices (if applicable)

Who Files GSTR-1?

Every GST-registered business with outward supplies must file GSTR-1, including:

• Shops, traders, manufacturers
• Service providers (consultants, agencies, contractors)
• E-commerce sellers

Monthly vs Quarterly Filing

| Turnover | Frequency |

|---|---|

| More than ₹5 Crore/year | Monthly (11th of next month) |

| Up to ₹5 Crore/year | Quarterly under QRMP scheme (13th of month after quarter) |

Step-by-Step: How to File GSTR-1

Step 1: Gather All Your Invoices

Collect every sales invoice you issued during the month. Make sure each invoice has:

• Unique invoice number (sequential, FY-wise)
• Customer GSTIN (for B2B sales)
• HSN/SAC code per line item
• Taxable value, GST rate, CGST/SGST or IGST amounts

> Pro Tip: If you use software like CafeMitra GST Billing, your invoices are already GST-compliant and pre-categorised into B2B and B2C. You can download a ready-to-file GSTR-1 Excel sheet directly from the Reports section, which matches the exact column format required on the GST portal.

Step 2: Login to the GST Portal

Go to [https://www.gst.gov.in](https://www.gst.gov.in) and login with your GSTIN and password.

Step 3: Navigate to GSTR-1

• Click Returns** → **Returns Dashboard
• Select the Financial Year and Tax Period (Month/Quarter)
• Click Prepare Online** or **Prepare Offline

Step 4: Fill in the Sections

Enter each invoice where the buyer has a valid GSTIN. Include:

• Customer GSTIN
• Invoice number and date
• Taxable value
• Place of Supply (State)
• Tax amounts (IGST for inter-state, CGST+SGST for intra-state)

These are invoices issued to non-GST customers but with a high value.

Report aggregate rate-wise totals. No individual invoice details needed.

Aggregate all line items by HSN code. Include:

• Total quantity
• Total taxable value
• Tax amounts (CGST, SGST, IGST)

This is mandatory for businesses with turnover > ₹5 Crore (4-digit HSN) and > ₹1.5 Crore (6-digit HSN).

Step 5: Preview and Submit

• Click Preview GSTR-1 PDF to review all entries
• If everything looks correct, click Submit
• After submitting, click File GSTR-1 with DSC (Digital Signature) or EVC (OTP-based)

Once filed, your GSTR-1 data is locked and your buyer's GSTR-2B (auto-populated ITC statement) will reflect your invoices.

Common Mistakes to Avoid

1. Wrong Place of Supply: For intra-state sales, use CGST+SGST. For inter-state (including exports), use IGST. Getting this wrong means your customer cannot claim ITC.

2. Missing HSN Codes: All line items must have HSN/SAC. Putting "Miscellaneous" or leaving it blank will result in a validation error.

3. Duplicate Invoice Numbers: Each invoice number must be unique within a financial year. Format recommended: `INV/2026-27/0001`

4. Filing Late: Late filing attracts ₹50/day penalty (₹20/day for nil returns). Don't miss the 11th of the month deadline.

5. Not Filing Nil Return: Even if you had zero sales in a month, you must file a Nil GSTR-1. Not filing at all is a compliance failure.

How CafeMitra Makes GSTR-1 Filing Easy

If you are running a business that issues 20-500 GST invoices a month, manually entering each one on the portal is painful and error-prone.

• Invoice auto-categorisation: Every invoice you create is automatically sorted into B2B or B2C based on whether the customer has a GSTIN.
• HSN auto-linking: Each product in your catalog has a pre-configured HSN code and GST rate. When you add it to an invoice, tax is calculated automatically.
• GSTR-1 Excel Export: Go to Reports → GSTR-1 Export. In one click, download an Excel file with 3 sheets — B2B, B2CS, and HSN Summary — formatted exactly as the GST portal offline tool requires.
• FY-aware invoice numbering: Invoices are automatically numbered `INV/2026-27/0001` onwards, resetting at the start of every financial year.
• 6-Month Free Offer: Start with 30 invoices free per month for 6 months, then upgrade to Pro (₹99/month) or Pro+ (₹199/month) for unlimited invoices.

Frequently Asked Questions

Yes, but you will pay a late fee. It's better to file on time even if some invoices are not ready — you can amend via GSTR-1A in the next period.

You can amend it in the next month's GSTR-1 using the amendment tables (4A, 5A, etc.).

Yes. You must file a Nil GSTR-1 by the due date.

GSTR-2B is your auto-populated Input Tax Credit statement. It is generated from your suppliers' GSTR-1. You don't file GSTR-2B; you only refer to it.

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*Managing your GST invoices, HSN codes and tax reports manually is a full-time job. CafeMitra GST Billing handles all of this automatically — so you can focus on running your business. [Try it free for 6 months](/login).*