How to File GSTR-1 Online: Complete Step-by-Step Guide 2026

What is GSTR-1 and Who Must File It

GSTR-1 is a statement of outward supplies required under Section 37 of the CGST Act, 2017, read with Rule 59 of the CGST Rules. Every registered person making outward supplies of goods or services must file GSTR-1, reporting invoice-level details of B2B sales, summary details of B2C sales, exports, credit and debit notes, advances received, and any amendments to previously filed data.

Who is exempt

Certain categories are not required to file GSTR-1. These include input service distributors (who file GSTR-6), composition scheme taxpayers (who file CMP-08 and GSTR-4), non-resident taxable persons (GSTR-5), persons deducting TDS under Section 51, and those collecting TCS under Section 52. If you hold a regular GSTIN and make taxable supplies, GSTR-1 applies to you even if you have nil sales in a period.

GSTR-1 Due Date in 2026

The GSTR-1 due date depends on your filing frequency.

Monthly filers

Taxpayers with aggregate annual turnover above Rs 5 crore, and those who have not opted for the quarterly scheme, must file GSTR-1 monthly. The due date is the 11th of the month following the tax period. For example, GSTR-1 for January 2026 is due by 11 February 2026.

Quarterly filers under QRMP

Taxpayers with aggregate turnover up to Rs 5 crore can opt for the Quarterly Return Monthly Payment (QRMP) scheme. Under QRMP, GSTR-1 is filed quarterly, with the due date being the 13th of the month following the quarter. For instance, the GSTR-1 for the January-March 2026 quarter is due by 13 April 2026.

Invoice Furnishing Facility (IFF)

QRMP taxpayers may use the IFF to upload B2B invoices for the first two months of a quarter, by the 13th of the following month. This is optional but helps your customers claim ITC promptly rather than waiting until the end of the quarter.

Documents and Information You Need

Before you begin filing, keep the following ready:

• All sales invoices for the tax period, separated into B2B (registered buyers) and B2C (unregistered consumers).
• GSTINs of all your B2B customers, verified for accuracy.
• Details of export invoices and shipping bill numbers, if applicable.
• Credit notes and debit notes issued during the period.
• Details of advances received and adjusted.
• HSN/SAC codes for your goods and services along with summary quantities and values.
• Your valid login credentials for the GST portal, or a DSC/EVC for verification.

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

Step 1: Log in to the GST portal

Visit the official GST portal and log in using your username and password. Navigate to Services, then Returns, then Returns Dashboard.

Step 2: Select the return period

Choose the relevant financial year, quarter, and month for which you are filing. Click Search to proceed.

Step 3: Open GSTR-1

Under the GSTR-1 tile titled Details of outward supplies of goods or services, click Prepare Online. Alternatively, use Prepare Offline if you wish to bulk-upload data via the offline utility tool, which is recommended for large volumes of invoices.

Step 4: Enter invoice details table by table

GSTR-1 is divided into several tables. Fill them as relevant:

• Table 4A, 4B: B2B invoices, entered invoice-wise with the buyer's GSTIN, invoice number, date, taxable value, and tax amounts.
• Table 5: B2C large invoices (inter-state supplies above the prescribed threshold to unregistered persons).
• Table 6: Exports and supplies to SEZ.
• Table 7: B2C others, entered as a consolidated summary rate-wise and state-wise.
• Table 8: Nil-rated, exempted, and non-GST supplies.
• Table 9: Amendments to invoices reported in earlier periods.
• Table 11: Advances received and adjusted.
• Table 12: HSN-wise summary of outward supplies.
• Table 13: Documents issued during the period.

Step 5: Use the offline utility for bulk data (optional)

For businesses with hundreds of invoices, download the GSTR-1 offline tool, populate the Excel template, generate a JSON file, and upload it under Prepare Offline. The portal will validate the file and flag any errors for correction.

Step 6: Generate summary and review

After entering all data, click Generate Summary. The portal computes the totals across all tables. Carefully review each section to ensure values match your books of accounts.

Step 7: File with DSC or EVC

Tick the acknowledgement checkbox, select the authorised signatory, and click File Statement. Companies and LLPs must use a Digital Signature Certificate (DSC), while other taxpayers can use an Electronic Verification Code (EVC) sent to the registered mobile and email. Once filed, an Acknowledgement Reference Number (ARN) is generated. Note that GSTR-1 cannot be revised once filed; corrections are only possible through amendments in a subsequent period.

How GSTR-1 Connects to Other Returns

The data you file in GSTR-1 auto-populates your GSTR-3B liability and forms the basis of your buyers' GSTR-2B, the auto-drafted ITC statement. Under Rule 36(4), buyers can claim ITC only to the extent reflected in their GSTR-2B, so timely and accurate GSTR-1 filing directly affects your customers' working capital. Additionally, the portal restricts filing of GSTR-1 if the previous period's return is pending, and persistent non-filing can lead to blocking of e-way bill generation.

Nil GSTR-1 Filing

If you had no outward supplies in a period, you must still file a Nil GSTR-1. The portal allows a simple Nil filing through the dashboard, and QRMP taxpayers can even file Nil returns via SMS to the designated number, making compliance quick and free of charge.

Late Fees and Penalties

Filing GSTR-1 after the due date attracts a late fee. The current structure prescribes a per-day late fee, subject to a maximum cap that varies by turnover slab. Nil returns attract a lower capped late fee. Beyond monetary penalties, delays harm your business relationships because buyers cannot claim ITC until your invoices appear in their GSTR-2B. Consistent late filing also affects your GST compliance rating.

Common Mistakes to Avoid

Entering incorrect GSTINs

A wrong or invalid buyer GSTIN means the invoice will not reflect in the correct party's GSTR-2B, denying them ITC. Always validate GSTINs before filing.

Mismatch between GSTR-1 and GSTR-3B

The taxable value and tax declared in GSTR-1 should reconcile with the liability paid in GSTR-3B. Differences trigger automated notices in Form DRC-01B. Reconcile both returns every period.

Forgetting to report credit and debit notes

Omitting credit notes overstates your liability, while missing debit notes understates it. Report all such documents in the period they were issued.

Wrong place of supply

Incorrectly classifying inter-state as intra-state supply (or vice versa) leads to wrong tax heads, IGST versus CGST/SGST. This is difficult to correct and may require amendments and refunds.

Ignoring HSN summary requirements

Reporting HSN codes at the required digit level is mandatory based on turnover. Skipping or incorrectly entering Table 12 can cause validation errors and notices.

Missing the IFF window

QRMP taxpayers who skip the IFF force their buyers to wait until quarter-end for ITC. Use the IFF for the first two months wherever your customers need timely credit.

Treating GSTR-1 as revisable

Many first-time filers assume they can edit a filed return. You cannot. Always review the generated summary thoroughly before clicking File, because corrections require amendment tables in future periods.

Tips for Smooth GSTR-1 Filing

Maintain a clean, GST-compliant invoicing system that captures GSTINs and HSN codes at the point of sale. Reconcile your sales register with the GSTR-1 summary before filing. File a few days ahead of the due date to avoid portal congestion. For multiple GSTINs or high invoice volumes, use the offline utility or a reliable GST software to reduce manual errors and save time.