GST Return Filing: Complete GSTR-1 and GSTR-3B Guide 2026

Filing GST returns is one of the most important compliance obligations for every registered taxpayer in India. Whether you are a small business owner or manage a large enterprise, understanding how to correctly file GSTR-1 (outward supply statement) and GSTR-3B (summary return with tax payment) is critical to avoiding penalties, maintaining your input tax credit eligibility, and keeping your business compliant.

This guide covers everything you need to know about GST return filing for FY 2026-27, including step-by-step filing instructions, due dates, the QRMP scheme, late fee calculations, and practical tips to streamline your compliance workflow.

What Are GSTR-1 and GSTR-3B?

GSTR-1 is a monthly or quarterly statement of outward supplies. It contains invoice-level details of all sales made during the period, including B2B transactions, B2C transactions, exports, credit and debit notes, and amendments to previously reported invoices. The data reported in GSTR-1 flows into the recipient's GSTR-2B, which determines their eligible input tax credit.

GSTR-3B is a self-assessed summary return that every regular taxpayer must file monthly or quarterly. It summarizes your total outward and inward supplies, input tax credit claimed, and the net tax payable. Unlike GSTR-1 which is a statement, GSTR-3B is the return where actual tax payment happens.

Key Differences Between GSTR-1 and GSTR-3B

GSTR-1 and GSTR-3B Due Dates for FY 2026-27

Monthly Filers (Turnover above Rs 5 crore)

Businesses with an aggregate annual turnover exceeding Rs 5 crore in the preceding financial year must file GSTR-1 and GSTR-3B on a monthly basis. The due dates are fixed throughout the year.

Quarterly Filers Under the QRMP Scheme (Turnover up to Rs 5 crore)

Taxpayers with aggregate turnover up to Rs 5 crore in the preceding financial year can opt for the Quarterly Return Monthly Payment (QRMP) scheme. Under this scheme, GSTR-1 and GSTR-3B are filed quarterly, but tax is paid monthly using the PMT-06 challan.

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

GSTR-1 requires you to report all outward supplies made during the tax period. Here is a detailed walkthrough of the filing process on the GST portal.

Step 1: Login and Navigate to GSTR-1

Go to gst.gov.in and log in with your GSTIN credentials. Navigate to Services > Returns > Returns Dashboard. Select the financial year and month/quarter, then click Prepare Online under GSTR-1.

Step 2: Report B2B Invoices (Table 4)

Enter details of all invoices issued to registered dealers (B2B). This includes the recipient GSTIN, invoice number, invoice date, taxable value, and applicable tax rates (CGST, SGST, IGST, cess). These details flow directly into the recipient's GSTR-2B for ITC claims.

Step 3: Report B2C Large Invoices (Table 5)

For inter-state supplies to unregistered dealers where the invoice value exceeds Rs 2.5 lakh, report the place of supply, invoice-level details, and tax amounts. These are categorized as B2C Large transactions.

Step 4: Report B2C Small Supplies (Table 7)

Intra-state supplies to unregistered dealers and inter-state supplies below Rs 2.5 lakh to unregistered dealers are reported here in a consolidated manner, state-wise with rate-wise summary.

Step 5: Report Credit and Debit Notes (Table 9)

Any credit notes or debit notes issued during the period against B2B invoices are reported here with reference to the original invoice. This adjusts the tax liability and the recipient's ITC.

Step 6: Export Invoices and Nil-Rated Supplies (Tables 6 and 8)

Report all export invoices (with or without payment of tax), supplies to SEZ units, and nil-rated or exempted supplies. Export invoices require the shipping bill number and date for claiming refunds.

Step 7: Amendments (Tables 9, 10, 11)

If you need to correct any details from a previously filed GSTR-1, use the amendment tables. You can amend B2B invoices, B2C inter-state invoices, credit/debit notes, and export invoices from prior periods.

Step 8: HSN Summary (Table 12)

Report an HSN-wise summary of all outward supplies. From FY 2026-27, HSN reporting at the 6-digit level is mandatory for taxpayers with turnover above Rs 5 crore, and 4-digit for those below Rs 5 crore.

Step 9: Preview and Submit

Review all the tables, cross-check totals, and click Submit. Once submitted, the data becomes frozen and auto-populates the recipient's GSTR-2B. Then file with DSC or EVC.

How to File GSTR-3B: Step-by-Step

GSTR-3B is where you pay your GST liability. It is a self-assessed return that summarizes your outward supplies, inward supplies (including reverse charge), ITC claimed, and net tax payable.

Step 1: Login and Navigate to GSTR-3B

Log in to gst.gov.in, go to Returns Dashboard, select the return period, and click Prepare Online under GSTR-3B.

Step 2: Report Outward Supplies (Table 3.1)

Enter the total value of outward supplies categorized as taxable supplies (other than zero-rated and reverse charge), zero-rated supplies, nil-rated and exempt supplies, and inward supplies liable to reverse charge. The system auto-populates values from your GSTR-1 data for reference.

Step 3: Report Inter-State Supplies (Table 3.2)

Provide state-wise details of inter-state supplies to unregistered persons and composition taxpayers. This is used for settlement of IGST between states.

Step 4: Claim Input Tax Credit (Table 4)

This is where you claim your ITC. Enter eligible ITC under IGST, CGST, SGST, and cess categories. The system shows auto-populated figures from GSTR-2B as a reference. You should reconcile your ITC with the GSTR-2B statement before filling this table. Check the ITC rules guide for detailed eligibility criteria.

Step 5: Report Exempt, Nil-Rated, and Non-GST Supplies (Table 5)

Enter details of exempt and nil-rated inward supplies, including those from composition dealers and non-GST supplies like petroleum products and alcohol.

Step 6: Calculate and Pay Tax (Table 6)

The system auto-calculates your tax liability based on Tables 3 and 4. Review the computation, then offset the liability using your ITC balance in the electronic credit ledger. Any remaining liability is paid through the electronic cash ledger by generating a challan.

Step 7: TDS/TCS Credit (Table 6.2)

If you have received TDS or TCS credits, these will be available in your electronic cash ledger. Verify and accept them before offsetting.

Step 8: Submit and File

Preview the return, verify all figures, then submit. Once submitted, the liability is computed and you can proceed to file with DSC or EVC. After filing, the return cannot be revised.

Late Fees and Penalties for Delayed Filing

Filing GST returns after the due date attracts both late fees and interest. Understanding the financial consequences helps you prioritize compliance deadlines.

Late Fee Structure

Interest on Late Payment

In addition to late fees, interest at 18% per annum is charged on the outstanding tax amount from the day after the due date until the date of actual payment. For excess ITC claimed, interest at 24% per annum applies.

Consequences of Non-Filing

• E-way bill blocking: After two consecutive missed GSTR-3B filings, your e-way bill generation is disabled under Rule 138E, preventing you from transporting goods.
• GST registration cancellation: If you do not file returns for six consecutive months, the tax officer may initiate cancellation proceedings for your GSTIN under Section 29(2).
• ITC denial for recipients: Non-filing of GSTR-1 means your buyers cannot claim ITC on the purchases they made from you, damaging your business relationships.
• Assessment proceedings: The department can issue a best judgment assessment under Section 62, estimating your liability based on available information.

Understanding the QRMP Scheme

The Quarterly Return Monthly Payment (QRMP) scheme was introduced to reduce the compliance burden for small taxpayers. Here is what you need to know to decide if it works for your business.

Eligibility

Any registered taxpayer with an aggregate turnover of up to Rs 5 crore in the preceding financial year can opt for the QRMP scheme. Taxpayers can opt in or out at the beginning of each quarter through the GST portal under Services > Returns > Opt-in for Quarterly Return.

Monthly Tax Payment Options

Under QRMP, you file returns quarterly but pay tax monthly for the first two months of the quarter. You can choose between two methods:

• Fixed Sum Method (FSM): Pay an amount equal to the tax paid in the last quarter divided by three, as a pre-filled challan.
• Self-Assessment Method (SAM): Calculate your actual liability for the month based on your inward and outward supplies and pay accordingly.

IFF (Invoice Furnishing Facility)

QRMP taxpayers can optionally upload B2B invoices in the first two months of the quarter through the IFF. This ensures your registered buyers can claim ITC monthly instead of waiting for your quarterly GSTR-1. The IFF is due on the 13th of the following month and is limited to invoices with a total value not exceeding Rs 50 lakh per month.

Common Mistakes to Avoid in GSTR-1 and GSTR-3B Filing

Even experienced accountants make errors that lead to notices, penalties, or ITC mismatches. Here are the most common pitfalls and how to avoid them.

1. Mismatch between GSTR-1 and GSTR-3B: The outward supply figures in GSTR-3B must align with the total reported in GSTR-1. Discrepancies trigger notices and may flag your account for scrutiny. Always reconcile both returns before filing.
2. Incorrect HSN codes: Using wrong HSN codes can lead to wrong tax rate application and attract penalties under Section 122. Verify HSN codes against the tariff schedule and ensure they are reported at the mandatory digit level.
3. Not reconciling ITC with GSTR-2B: Claiming ITC in GSTR-3B without verifying it against the auto-populated GSTR-2B statement can result in excess credit claims, attracting interest at 24% per annum and possible penalty.
4. Filing GSTR-3B before GSTR-1: This can create data inconsistencies. Always file GSTR-1 first so the auto-populated values in GSTR-3B reflect accurate data.
5. Forgetting to report amendments: Corrections to prior period invoices must be reported in the amendment tables of GSTR-1. Missing these leads to permanent mismatches in the GST system.
6. Not filing Nil returns: Even if you have no transactions, you must file Nil returns. Not filing attracts late fees and can lead to registration cancellation.
7. Ignoring the IFF under QRMP: While optional, not using the IFF hurts your B2B customers who need monthly ITC. It can affect your business relationships with registered buyers.

Tips for Efficient GST Return Filing

Managing GST compliance efficiently saves time, reduces errors, and minimizes your risk of penalties. Here are practical strategies used by compliant businesses.

• Maintain a compliance calendar: Set reminders for all due dates well in advance. Use digital tools to track deadlines across GSTR-1, GSTR-3B, GSTR-9, and other returns.
• Reconcile monthly, not at year-end: Match your purchase register with GSTR-2B every month. This prevents large mismatches from accumulating and makes the annual return (GSTR-9) much easier.
• Use the JSON upload facility: For businesses with high invoice volumes, preparing data offline and uploading via JSON or through accounting software integrations is faster and less error-prone than manual entry on the portal.
• Separate intra-state and inter-state transactions: Maintain clear records of whether supplies are intra-state (CGST + SGST) or inter-state (IGST) from the invoicing stage itself to avoid classification errors.
• Review auto-populated data critically: While the GST portal auto-populates certain values in GSTR-3B from GSTR-1 and GSTR-2B, always verify these against your own books before accepting them.
• File early, not on the due date: The GST portal experiences heavy traffic on due dates, leading to timeouts and errors. Filing 3-5 days before the deadline avoids these issues.

Frequently Asked Questions