GSTR-1 Filing Guide 2026: Due Dates, Filing Process, Format & Late Fees

What Is GSTR-1?  Due Dates, Filing Process, Format and Late Fees (2026)

GSTR-1 is the monthly or quarterly return every regular GST-registered business uses to report its outward supplies, meaning sales, exports, credit notes, and debit notes for a tax period. It is filed on the GST portal before GSTR-3B, and the invoice details it carries decide whether your buyers can claim input tax credit. If you sell goods or services under GST, filing GSTR-1 correctly and on time is one of the most basic compliance tasks on your calendar.

This guide covers who must file GSTR-1, the current due dates for 2026, the exact format and tables inside the return, the filing steps on the GST portal, and what late filing actually costs you.

What Is GSTR-1?

GSTR-1 is the statement of outward supplies filed under Section 37 of the CGST Act. It records outward supply information such as sales invoices, exports, debit and credit notes, nil-rated or exempt supplies, advances received, and HSN-wise summaries of transactions. Once you submit it, the details cannot be edited within the same return. Corrections carry forward to the next period's return or, where applicable, to GSTR-1A.

Because GSTR-1 data flows into your buyers' GSTR-2B, an error or a delay on your side does not just affect your own compliance record. It can hold up the input tax credit your customers are entitled to claim, which is often the real cost of a late or sloppy filing.

Who Should File GSTR-1?

Every regular taxpayer registered under GST has to file GSTR-1, including businesses with zero sales in a given period. If there were no outward supplies during the tax period, a Nil GSTR-1 still needs to be filed. Skipping it because "there was nothing to report" is a common and avoidable mistake.

A few categories of taxpayers file different forms instead of GSTR-1:

• Composition scheme dealers file CMP-08 quarterly and GSTR-4 annually
• Input Service Distributors file GSTR-6
• Non-resident taxable persons file GSTR-5
• OIDAR service providers file GSTR-5A
• E-commerce operators liable for TCS file GSTR-8

Everyone else registered under the GST Act, whether they had transactions or not, falls under the GSTR-1 filing requirement.

GSTR-1 Due Date 2026: Monthly and Quarterly (QRMP)

Your GSTR-1 due date depends on your turnover and the filing frequency you have opted for.

Monthly filers, including those who voluntarily choose to file monthly, must file by the 11th of the following month, while quarterly filers under QRMP must file by the 13th of the month after the quarter ends.

Businesses on the QRMP scheme still need to report B2B invoice data every month, not just once a quarter. Even under QRMP, B2B invoices have to be entered each month through the Invoice Furnishing Facility (IFF) by the 13th of each month for the first two months of the quarter, so buyers can claim their input tax credit without delay. The IFF is optional, but skipping it means your B2B buyers wait until your quarterly GSTR-1 to see those invoices in their GSTR-2B.

You can switch in or out of QRMP once every quarter, between the 1st and the last day of the first month of that quarter.

Due dates can be extended by the government through official CBIC notifications, and an extension does not always apply to every taxpayer category or state. Always confirm the exact due date for your GSTIN on the GST portal before filing rather than relying on a general calendar.

GSTR-1 Format: What Each Table Covers

GSTR-1 is broken into tables, each covering a different type of outward supply. The ones that matter for most businesses are:

• B2B invoices (Table 4): sales to GST-registered buyers, reported invoice by invoice
• B2C large invoices, Table 6: inter-state sales above ₹2.5 lakh to unregistered buyers
• B2C others, Table 7: the rest of your unregistered-buyer sales, reported as state-wise totals
• Credit and debit notes: adjustments against invoices already reported
• Exports (Table 6A): zero-rated supplies, with or without payment of tax
• Nil-rated, exempt and non-GST supplies
• Advances received and adjusted
• HSN-wise summary (Table 12): since May 2025, this table is split into two separate tabs, one for B2B supplies and one for B2C supplies, and HSN codes are selected from a dropdown rather than typed in manually

Businesses now report HSN summary details for B2B and B2C supplies separately in Table 12 of GSTR-1. If your turnover is up to ₹5 crore you report 4-digit HSN codes; above that threshold, 6-digit codes are required. HSN reporting is mandatory on the B2B tab and optional on the B2C tab for businesses under the ₹5 crore threshold. Note that Table 12A (B2B) generally needs at least one entry even if you have no B2B sales for the period, since the portal can throw a validation error otherwise; the workaround is to enter any valid HSN code with all value fields set to zero.

Most B2B invoices and eligible credit or debit notes are now auto-populated from the e-invoicing system, so your job is largely to verify the auto-filled data against your books rather than key it in from scratch.

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

Filing GSTR-1 on the GST portal follows a fairly standard sequence, though the exact screens vary slightly by return period.

1. Log in to the GST portal at gst.gov.in using your GSTIN credentials.
2. Go to Returns Dashboard, select the financial year and the tax period, and choose GSTR-1/IFF.
3. Enter or upload invoice data into the relevant tables based on the type of supply (B2B, B2C, exports, credit/debit notes, and so on). Bulk uploads via JSON or offline utility tools work well if you have a high invoice volume.
4. Check auto-populated e-invoice data. Verify that IRN-linked invoices in the system match your own records before making manual edits.
5. Validate GSTINs, invoice numbers and tax calculations before moving forward. An inactive or mistyped buyer GSTIN means that invoice will not show up in their GSTR-2B.
6. Review the summary the portal generates for all tables and reconcile it against your sales register.
7. Submit and file using DSC or EVC, after paying any applicable late fee shown by the system.

For nil returns, there is a faster route: you can file a Nil GSTR-1 by SMS, receive a 6-digit OTP, and confirm by replying with a specific text, without logging into the portal at all.

GSTR-1 Late Fee and Penalty

The GST portal will not let you file GSTR-1 without first clearing any late fee due, and the fee accrues automatically for every day past the due date.

If you file GSTR-1 five days after the due date, the late fee works out to ₹250, calculated as ₹50 multiplied by 5 days, and it cannot exceed ₹5,000 no matter how long the delay runs. A nil return attracts a much smaller ₹20 per day, capped at ₹500.

A few points that catch people out:

• The late fee applies even to nil returns filed after the due date. Zero sales does not mean zero consequence for filing late.
• Late fee for GSTR-1 is separate from interest. Interest at 18% per annum applies only to unpaid tax, not to the return filing itself, and GSTR-1 has no tax payment attached to it directly since tax is paid through GSTR-3B.
• You cannot file any GSTR-1 more than three years past its original due date; as of 2026 the portal permanently blocks these older returns. Consistent late filing is not a "catch up later" problem indefinitely.
• Failure to file GSTR-1 for extended periods, on top of the late fee, blocks your ability to file subsequent returns and can affect GST registration status.

GSTR-1 vs GSTR-3B: What's the Difference?

GSTR-1 and GSTR-3B are often confused because both are filed every month or quarter, but they do different jobs.

GSTR-1 is about disclosure, it tells the system and your buyers what you sold. GSTR-3B is about settlement, it is where you actually pay tax based on a summary of outward and inward supplies. The two need to reconcile with each other; a mismatch between them is one of the most common triggers for a GST notice.

What Is GSTR-1A?

GSTR-1A is a relatively recent addition that lets you amend GSTR-1 details for the current period before you file GSTR-3B, instead of waiting for the next period's return. If your GSTR-1 has an error, an invoice value that's wrong, or a missing entry, GSTR-1A gives you a window to fix it within the same cycle rather than carrying the mistake into GSTR-3B and reconciling it later.

Documents Required to File GSTR-1

You need a valid GSTIN, your GST portal login credentials, and either a digital signature certificate or the ability to e-sign the return, along with your Aadhaar-linked mobile number if you are e-signing. Beyond the login essentials, keep your sales register, invoice-level data for the period, and any credit or debit notes issued ready before you sit down to file, since reconciling these against the portal's auto-populated data is most of the actual work.

Common Mistakes to Avoid While Filing GSTR-1

• Skipping the nil return. No sales in a period still requires a filing, and the late fee applies even here.
• Wrong invoice classification. Reporting a registered buyer's invoice under B2C instead of B2B means that buyer never sees it in their GSTR-2B and cannot claim ITC. This happens most often when the billing team does not collect the buyer's GSTIN at the point of sale.
• Misclassifying exports in the HSN summary. Exports belong under the B2C category in Table 12, even when the foreign buyer holds a GSTIN, since GSTIN only applies to Indian recipients.
• Leaving Table 12A blank when you have only B2C sales. This can trigger a validation error; enter one HSN line with zero values as a workaround.
• Not reconciling with GSTR-2B or e-invoice data before submission, which leads to mismatches that surface later as notices.
• Filing GSTR-3B before fixing known GSTR-1 errors, when GSTR-1A could have corrected them first.

Benefits of Filing GSTR-1 on Time

Filing on schedule is not just about avoiding the late fee. Timely GSTR-1 filing lets your reconciliation between your GSTR-1 and your suppliers' or buyers' GSTR-2B happen without last-minute scrambling, keeps your compliance rating clean, and protects your buyers' ability to claim input tax credit without chasing you for corrections. A consistent filing record also matters if you ever apply for loans, tenders, or GST registration amendments, since a clean compliance history is something lenders and larger clients increasingly check.

Frequently Asked Questions on GSTR-1

1. What is GSTR-1 in GST?

GSTR-1 is the return where a registered taxpayer reports all outward supplies, meaning sales, exports, and related credit or debit notes, for a given tax period.

2. What is the due date for GSTR-1 in 2026?

Monthly filers must file by the 11th of the following month. QRMP quarterly filers must file by the 13th of the month after the quarter ends, unless the government issues a specific extension.

3. Is GSTR-1 filing mandatory even with no sales?

Yes. A Nil GSTR-1 must be filed even if there were no outward supplies during the period. It can be filed on the portal or through the SMS-based nil filing option.

4. What is the late fee for GSTR-1?

₹50 per day (₹25 CGST plus ₹25 SGST) for regular returns, capped at ₹5,000. For nil returns, it is ₹20 per day, capped at ₹500.

5. Can GSTR-1 be revised after filing?

No, GSTR-1 itself cannot be revised once filed. Corrections are made either through GSTR-1A for the same period, before GSTR-3B is filed, or carried into the next period's GSTR-1.

6. What is the difference between GSTR-1 and GSTR-3B?

GSTR-1 reports outward supply details invoice by invoice and involves no tax payment. GSTR-3B is a summary return where actual tax liability is paid, and it is filed after GSTR-1.

7. Who is exempt from filing GSTR-1?

Composition dealers, Input Service Distributors, non-resident taxable persons, OIDAR providers, and e-commerce operators liable for TCS file separate forms (CMP-08/GSTR-4, GSTR-6, GSTR-5, GSTR-5A, and GSTR-8 respectively) instead of GSTR-1.

8. What is the QRMP scheme and how does it affect GSTR-1?

QRMP lets businesses with turnover up to ₹5 crore file GSTR-1 once a quarter instead of monthly, while still paying tax monthly through PMT-06 and optionally reporting B2B invoices monthly via the IFF.

9. What is the Invoice Furnishing Facility (IFF)?

IFF lets QRMP taxpayers upload B2B invoice details for the first two months of a quarter, so their registered buyers can claim ITC without waiting for the quarterly GSTR-1.

10. How do I file a nil GSTR-1?

You can file it on the GST portal by selecting nil filing for the period, or through SMS by sending the required nil-filing text and confirming with the OTP you receive.

11. What happens if GSTR-1 is not filed for a long time?

Beyond the accumulating late fee, prolonged non-filing can block your ability to file future returns and, in the case of GSTR-1 filings pending more than three years past the original due date, the portal now blocks those returns permanently.

12. Does GSTR-1 attract interest along with the late fee?

No interest applies to GSTR-1 itself, since no tax is paid with this return. Interest at 18% per annum applies to unpaid tax reported and paid late through GSTR-3B.

13. How is HSN summary reported in GSTR-1 now?

Since the May 2025 tax period, Table 12 is split into separate B2B and B2C tabs, HSN codes are chosen from a dropdown, and the digit requirement (4 or 6) depends on your turnover.

14. Can exports be reported as B2B in the HSN summary?

No. Exports are reported under the B2C category in Table 12, even if the overseas buyer has a tax identification number, because GSTIN applies only to Indian recipients.

15. What is GSTR-1A used for?

GSTR-1A lets a taxpayer correct or add outward supply details for the current period before filing GSTR-3B, instead of waiting to fix the error in the next period's GSTR-1.

16. Who needs to file GSTR-1 monthly versus quarterly?

Businesses with turnover above ₹5 crore, or those who voluntarily opt for monthly filing, file GSTR-1 monthly. Businesses with turnover up to ₹5 crore can opt for quarterly filing under QRMP.

17. Is HSN reporting mandatory for B2C supplies?

Not currently, for businesses below ₹5 crore turnover. It is mandatory for B2B supplies regardless of turnover slab, with the digit length depending on turnover.