GST Returns & Invoices for Online Sellers

Updated 6 November 2026 · Standard formula, shown below

Registering for GST as an online seller means you now have monthly/quarterly filing obligations and must issue compliant tax invoices. This guide walks you through the entire process—from creating correct invoices to filing your returns—so you stay compliant and avoid penalties.

What You’ll Need

Your GSTIN (GST Identification Number) and login credentials for the GST portal
Sales records for the period (order reports from your marketplace or your own records)
Purchase invoices with valid GST (for input tax credit)
Bank statements or payment gateway reports to reconcile sales
Your HSN code for the products you sell (find it in your GST registration)

Step-by-Step

Generate a tax invoice for every sale. For B2B sales (to registered businesses), issue a full GST invoice with your name, GSTIN, buyer’s name and GSTIN, invoice number, date, description, HSN code, quantity, taxable value, GST rate, and the GST amount split into CGST and SGST (or IGST for inter-state sales). For B2C sales (to consumers), you can issue a simplified invoice with fewer details, but it must still show the total and GST charged.
Record all sales in a register. Maintain a sales register (Excel or accounting software) with invoice number, date, buyer details, taxable value, GST rate, and GST amount. This will be your source for GSTR-1.
File GSTR-1 (outward supplies) by the 11th of the following month. Log in to the GST portal, go to Services > Returns > GSTR-1, and enter your sales details. You can upload a JSON file or enter manually. For small sellers, the quarterly filing option (QRMP) is available if your turnover is below ₹5 crore—then you file GSTR-1 quarterly but pay tax monthly via GSTR-3B.
File GSTR-3B (summary return) by the 20th of the following month. This is a simple summary of total sales, tax payable, and input tax credit claimed. Enter the totals from your sales register and purchase register. Pay any tax due via the portal’s payment options.
Claim input tax credit (ITC) on purchases. Ensure your suppliers have filed their returns and you have valid invoices. The ITC will reflect in GSTR-2B (auto-drafted). In GSTR-3B, enter the eligible ITC amount. Keep all purchase invoices safe for at least 6 years.
Reconcile your sales with payment gateways. At month-end, match your sales register with the amounts credited to your bank account (net of gateway fees) to catch discrepancies.
File annual return (GSTR-9) if your turnover exceeds ₹2 crore. This is due by 31st December of the next financial year. It consolidates all monthly/quarterly returns.
Keep track of deadlines. Mark the 11th and 20th of every month on your calendar. Late filing attracts a penalty of ₹50 per day (₹20 for NIL returns) plus interest at 18% per annum.

Common Mistakes

Mixing up CGST/SGST and IGST. For intra-state sales, split the tax equally into CGST and SGST. For inter-state, charge IGST. Using the wrong type leads to mismatches.
Wrong HSN codes. Using an incorrect HSN can lead to wrong tax rates. Verify the code for your product before invoicing.
Forgetting to mention GSTIN on invoices. If you are B2B and the buyer’s GSTIN is missing, the buyer cannot claim ITC, and you may face issues.
Not filing GSTR-1 on time. Even if you have no sales, you must file a NIL return. Late filing blocks your ability to file GSTR-3B and pay tax.
Claiming ITC without valid invoices. If your supplier hasn’t filed returns, you cannot claim ITC. Always verify that the supplier’s GSTIN is active.
Ignoring credit notes. If you issue a refund or credit note, you must report it in GSTR-1 to reduce your tax liability. Missing this can overstate your tax.

Tips

Use accounting software like Tally, Zoho, or QuickBooks that integrates with GST. It auto-generates invoices and GSTR-1 files, reducing errors.
Set up a separate bank account for business transactions to simplify reconciliation.
Keep a digital copy of every invoice in a cloud folder. You’ll need them for reconciliation and if the tax department asks for verification.
For marketplaces (Amazon, Flipkart, etc.), download their monthly GST reports—they often have ready-to-use data for GSTR-1.
Reconcile ITC monthly. Compare GSTR-2B with your purchase register to spot missing invoices early.
Consider the composition scheme if your turnover is below ₹1.5 crore (₹75 lakh for services). It reduces compliance but you cannot claim ITC or issue tax invoices.

Troubleshooting

GSTR-1 mismatch with GSTR-3B: If your GSTR-1 and GSTR-3B totals don’t match, the portal will show an error. Review your sales register for missing entries or duplicate invoices. Correct the return before the due date.
ITC not reflecting in GSTR-2B: Ask your supplier to file their GSTR-1. If they haven’t, you cannot claim ITC. You can also check if the invoice was uploaded correctly.
Forgot to file a return: You can file a late return on the portal, but you’ll have to pay late fees and interest. Do it immediately to avoid further penalties.
Portal login issues: Reset your password via the ‘Forgot Password’ link. If the portal is down, wait and try during off-peak hours (early morning).
Invoice rejected by buyer: If a buyer says your invoice is invalid, check the GSTIN format and your HSN code. Reissue a corrected invoice.

Frequently Asked Questions

Do I need to issue an invoice for every sale, even to consumers?

Yes, you must issue a tax invoice for every taxable supply, regardless of the buyer type. For B2C, a simplified invoice is acceptable.

Can I file GSTR-1 quarterly?

Yes, if your turnover is below ₹5 crore, you can opt for the QRMP scheme and file GSTR-1 quarterly. However, you must still pay tax monthly via GSTR-3B.

What is the penalty for late filing?

Late filing attracts a late fee of ₹50 per day (₹20 for NIL returns) plus interest at 18% per annum on the tax due. The maximum late fee is capped at ₹10,000 per return.

Can I claim input tax credit on purchases from unregistered dealers?

No, you can only claim ITC on purchases from registered suppliers who have filed their returns and reflected the invoice in GSTR-1.

How do I handle returns/refunds?

Issue a credit note to the buyer and report it in GSTR-1. This will reduce your taxable sales and tax liability for that period.

What if I sell through multiple marketplaces?

Each marketplace will provide a GST report. You need to consolidate all sales into a single GSTR-1. Ensure you have separate GSTINs for each state if you have physical presence in multiple states.

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.