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

If you're registered under GST, GSTR-1 is one return you can't skip - even in a month with zero sales. It's the return where you declare every sale you made, and it's the foundation that everything else in the GST return cycle builds on. Get GSTR-1 wrong, and the errors ripple straight into GSTR-3B and into your buyers' input tax credit claims.

Here's a clear, practical breakdown of what GSTR-1 is, when it's due, who's exempt, what happens if you're late, and how to keep the whole process from becoming a monthly fire drill.

What Exactly Is GSTR-1?

GSTR-1 is a return of outward supplies - in plain terms, a statement of everything you sold in a tax period. It covers B2B invoices, B2C sales, exports, credit and debit notes, advances received, and a few other categories, spread across multiple tables in the return.

Most B2B invoice data now flow in automatically if you're generating e-invoices, which cuts down manual entry. But B2C sales, reverse-charge transactions, HSN-wise summaries, and any amendments to past invoices still need your attention.

Why does this return matter so much? Because the sales data you report here becomes the basis for:

• Your own GSTR-3B - the summary return where you declare tax liability and offset it against credits
• Your buyers' GSTR-2B - the auto-drafted credit statement your customers rely on to claim input tax credit

If your GSTR-1 has missing invoices, wrong GSTINs, or incorrect tax amounts, your customers may not get the credit they're owed - and that's the kind of thing that damages business relationships fast.

GSTR-1 Due Dates: Monthly vs Quarterly

Your filing frequency depends on turnover and whether you've opted into the QRMP (Quarterly Return Monthly Payment) scheme.

If you're on QRMP, you're not entirely off the hook every month - you still need to upload B2B invoices for the first two months of the quarter through the Invoice Furnishing Facility (IFF) if you want your buyers to see them in time for their own credit claims. The full quarterly GSTR-1 covers the invoices for all three months, with the third month's invoices reported directly in the quarterly return itself.

A rule worth flagging: returns more than three years past their original due date can no longer be filed at all - this time bar was written into Section 37 of the CGST Act and the GST portal now enforces it. There's no case for "I'll catch up later" anymore; old pending returns can become permanently unfileable.

Who Doesn't Need to File GSTR-1?

Filing GSTR-1 is mandatory for every GST-registered person for every tax period, including nil filings - but a handful of registration types are excluded because they file different returns entirely:

• Input Service Distributors (ISD)
• Composition scheme dealers (they file CMP-08 instead)
• Suppliers of OIDAR services (online information and database access services) who pay tax directly
• Non-resident taxable persons
• Persons required to collect TCS
• Persons required to deduct TDS under GST

Everyone else files - sales or no sales.

Nil Returns Are Still Returns

A common misconception is that no sales means no filing obligation. That's incorrect. If you had zero outward supplies in a tax period, you still file a Nil GSTR-1. Nil filing can be done quickly through the portal, and an SMS-based nil filing facility has also been available for a few years now for taxpayers who prefer that route.

Can You Fix a Mistake After Filing?

Once GSTR-1 is filed, it's locked - there's no straightforward "revise and resubmit" like a bank statement correction. Instead, corrections go through GSTR-1A, a facility introduced specifically to let you amend invoice details or add missed invoices for the same tax period.

The catch: GSTR-1A must be filed before you file GSTR-3B for that period. Once GSTR-3B is filed, that window closes for the period in question, and any further correction has to wait for a later period's return through the standard amendment tables.

It's also worth remembering that since January 2022, GSTR-1 must be filed before GSTR-3B for the same period - you can't file them out of sequence.

Late Fees: What Delay Actually Costs You

Missing the due date isn't the end of the world, but it isn't free either. Late fees accrue per day of delay, split between CGST and SGST/UTGST, with a turnover-based cap:

These caps have been reduced over time from the original ?200/day structure, as part of relief measures for taxpayers - but the fee still adds up quickly if a return sits unfiled for weeks, so it's not something to treat casually.

A Few Recent Procedural Changes Worth Knowing

GST return filing isn't static, and a couple of relatively recent clarifications are worth keeping in mind:

• HSN entry is now selection-only. Manual typing of HSN codes in Table 12 was phased out in favour of choosing from a dropdown list, and the table itself was split into separate B2B and B2C sections for cleaner reporting.
• Table 12A can't be left completely blank, even for taxpayers with only B2C supplies. If there's no B2B supply to report, the guidance is to enter at least one HSN/UQC line with zero values, rather than leaving the section empty.

These are small process details, but they're the kind of thing that trips up manual filers far more than businesses running on automated GST software, where such validations are typically built into the workflow.

Where Manual GSTR-1 Filing Tends to Break Down

For businesses with high invoice volumes, multiple GSTINs, or frequent amendments, the real challenge with GSTR-1 usually isn't understanding the rules - it's execution at scale:

• Reconciling invoice data across ERPs, e-invoicing portals, and the GST system
• Catching mismatches before they become buyer-facing credit disputes
• Managing amendments across the right tables without breaking the GSTR-1A window
• Tracking due dates across multiple GSTINs with different filing frequencies

This is where GST compliance software earns its keep - not by changing the rules, but by removing the manual reconciliation and deadline-tracking overhead that causes most filing errors in the first place.

How Taxilla Handles This

Taxilla's GST compliance platform is built around the exact pain points above:

• Auto-populated invoice data pulled directly from your ERP or e-invoicing setup, so B2B tables in GSTR-1 don't need manual re-entry
• Built-in validation before filing - mismatched GSTINs, missing HSN codes, and blank-table errors (like the Table 12A issue above) get flagged before you hit submit, not after the portal rejects it
• Multi-GSTIN dashboards for businesses filing across multiple states, so nothing slips through because it was tracked in a separate spreadsheet
• GSTR-1 to GSTR-3B reconciliation built in, so the sequencing rule (GSTR-1 before GSTR-3B) and the numbers matching between the two aren't something your team has to check by hand every cycle
• Deadline alerts tuned to whether you're on monthly or QRMP filing, so the 11th vs 13th distinction is handled automatically rather than tracked manually

If you're currently reconciling GSTR-1 data manually across spreadsheets and portal uploads, [see how Taxilla automates GST return filing ?]

Frequently Asked Questions

Do I need to file GSTR-1 if I had no sales?

Yes. You must file a Nil GSTR-1 for that period - there's no exemption for zero-transaction months.

Can I file GSTR-1 after the due date?

Yes, but a late fee applies based on the number of days delayed, subject to the caps outlined above.

What's the difference between GSTR-1 and GSTR-3B?

GSTR-1 reports invoice-level sales detail. GSTR-3B is a summary return where you declare total tax liability, claim input tax credit, and make the actual tax payment.

Can I file GSTR-1 after GSTR-3B for the same period?

No. Since January 2022, GSTR-1 must be filed before GSTR-3B for that tax period.

I'm on the composition scheme - do I file GSTR-1?

No. Composition dealers file CMP-08 for quarterly tax payments instead of GSTR-1.

How do I correct an invoice after filing GSTR-1?

Through GSTR-1A, filed for the same tax period, and only before GSTR-3B for that period is filed.

Filing GSTR-1 correctly, on time, and without last-minute reconciliation scrambles gets a lot easier when the invoice data, validations, and deadlines are handled by one system instead of pieced together across ERPs and spreadsheets. That's the gap Taxilla's GST compliance platform is built to close - Explore Taxilla's GSTR-1 automation