What is GSTR-1?
GSTR-1 is the return where you report all your outward supplies (sales) for a tax period. Every invoice you issued during the month (or quarter) gets reported here — B2B invoices with buyer's GSTIN, B2C sales, exports, credit notes, debit notes, and advances received.
Here's why GSTR-1 matters so much: your buyer's Input Tax Credit depends on it. When you report a B2B invoice in your GSTR-1, it flows into your buyer's GSTR-2B. If you don't file GSTR-1 or miss an invoice, your buyer can't claim ITC on that purchase. That makes them unhappy, and unhappy buyers look for other suppliers.
Think of GSTR-1 as the foundation of the entire ITC chain in GST. If outward supply data isn't reported correctly, everything downstream breaks — ITC matches fail, reconciliation mismatches appear, and both you and your buyer end up explaining things to the department.
Who Needs to File GSTR-1?
Every registered taxpayer who makes outward supplies must file GSTR-1. This includes:
- Regular taxpayers (monthly or quarterly filers)
- Casual taxable persons
- SEZ developers and units
- E-commerce operators (for supplies made through their platform)
Who doesn't file GSTR-1?
- Composition dealers (they don't issue tax invoices)
- Input Service Distributors (they file GSTR-6)
- Non-resident taxable persons (they file GSTR-5)
- TDS/TCS deductors and collectors
Filing Frequency and Due Dates
| Category | Frequency | Due Date | |---|---|---| | Turnover > ₹5 crore in previous FY | Monthly | 11th of the next month | | Turnover ≤ ₹5 crore (opted for QRMP) | Quarterly | 13th of month after quarter | | Turnover ≤ ₹5 crore (opted for monthly) | Monthly | 11th of the next month |
QRMP quarterly filers must still use the Invoice Furnishing Facility (IFF) to upload B2B invoices in the first two months of each quarter. IFF lets your buyers see invoices in their GSTR-2B without waiting for your quarterly GSTR-1.
Tables in GSTR-1 — What Goes Where
GSTR-1 has multiple tables. Don't panic — most businesses only use 3-4 of them regularly:
Table 4 — B2B Invoices (Taxable)
This is the main table for most businesses. Report every tax invoice issued to registered buyers (those with GSTIN). For each invoice, you enter:
- Buyer's GSTIN
- Invoice number and date
- Invoice value (total including tax)
- Taxable value and rate-wise GST breakup
- Place of supply
- Whether it's a reverse charge invoice
Important: E-invoices (for businesses with turnover > ₹5 crore) are auto-populated in Table 4 from the IRP. You don't need to enter them manually — they flow in automatically.
Table 5 — B2B Invoices to Unregistered Persons (Inter-State > ₹2.5 Lakh)
If you sold goods/services worth more than ₹2.5 lakh to an unregistered buyer in another state, report it here. Intra-state B2C supplies and inter-state B2C supplies under ₹2.5 lakh go to Table 7.
Table 6 — Exports and Deemed Exports
All export invoices — both with payment of IGST and under bond/LUT (Letter of Undertaking). Enter shipping bill number, port code, and other export details.
Table 7 — B2C (Others)
The catch-all for smaller B2C supplies: all intra-state B2C sales (any value), and inter-state B2C sales up to ₹2.5 lakh. These are reported as state-wise, rate-wise summary totals — not individual invoices.
Table 8 — Nil Rated, Exempted, and Non-GST Supplies
Summary of supplies where GST doesn't apply: nil-rated goods, exempted supplies, and non-GST items (like petroleum, alcohol). Broken into registered vs unregistered recipients.
Table 9 — Credit Notes and Debit Notes
Any credit notes or debit notes issued during the period. Link each to the original invoice number. Credit notes reduce your liability; debit notes increase it.
Table 11 — Advances Received
If you received advance payments against which you issued a receipt voucher but haven't yet raised an invoice, report the advance here with applicable GST. Once you issue the invoice, the advance adjusts in Table 11A.
Table 12 — HSN-wise Summary
A summary of all outward supplies by HSN code. Mandatory for:
- Turnover > ₹5 crore: 6-digit HSN codes
- Turnover ≤ ₹5 crore: 4-digit HSN codes
Step-by-Step: Filing GSTR-1 on the Portal
Step 1: Login and Select the Period
Go to gst.gov.in → Login → Services → Returns → Returns Dashboard. Select the financial year and period (month or quarter). Click Search, then click Prepare Online next to GSTR-1.
Step 2: Enter B2B Invoices (Table 4)
Click on 4A, 4B, 4C, 6B, 6C — B2B Invoices. Add the buyer's GSTIN. The system will auto-populate their trade name. Enter each invoice:
- Invoice number (exactly as printed on the invoice)
- Invoice date
- Total invoice value
- Place of supply (state)
- Supply type (regular, SEZ with/without payment, deemed export)
- Taxable value and GST rate
Add all invoices for the period. If you have e-invoices, these are already auto-populated — verify and confirm them.
Step 3: Enter B2C Sales (Tables 5 and 7)
For large inter-state B2C (> ₹2.5 lakh) — add individual invoices in Table 5. For all other B2C — add state-wise and rate-wise summary totals in Table 7.
Step 4: Add Credit/Debit Notes (Table 9)
Click on 9B — Credit/Debit Notes (Registered). For each note:
- Note type (Credit or Debit)
- Note number and date
- Original invoice number (link it)
- Taxable value and tax amounts
Step 5: Add HSN Summary (Table 12)
Click on 12 — HSN-wise Summary. Add HSN codes, descriptions, UQC (unit), quantity, taxable value, and tax amounts. This is a summary — not invoice-level detail.
Step 6: Preview and Submit
Click Preview to see the entire GSTR-1 summary. Check totals against your sales register. If everything matches, click Submit. After submission, you can still make changes to certain fields until you file.
Step 7: File with DSC/EVC
After submission and review, click File GSTR-1 with Digital Signature Certificate (DSC) or Electronic Verification Code (EVC/OTP). Once filed, it's final for the period — no revisions allowed.
GSTR-1 vs IFF — Understanding the Difference
If you're on the QRMP scheme (quarterly filing), you don't file GSTR-1 every month. But your buyers need to see your invoices monthly. That's where Invoice Furnishing Facility (IFF) comes in:
| Feature | GSTR-1 | IFF | |---|---|---| | Who uses it | Monthly filers + quarterly filers (end of quarter) | Quarterly filers (months 1 & 2 of quarter) | | What's reported | All supplies (B2B + B2C + exports + CN/DN) | Only B2B invoices (up to ₹50 lakh per month) | | Due date | 11th (monthly) or 13th (quarterly) | 13th of next month | | Impact on buyer | Flows to buyer's GSTR-2B | Flows to buyer's GSTR-2B |
Pro tip: If you're a quarterly filer and your B2B customers complain about ITC not reflecting, use IFF in months 1 and 2. It solves the problem without switching to monthly filing.
Common Mistakes in GSTR-1
1. Wrong GSTIN of Buyer
Even one digit wrong means the invoice goes to the wrong GSTIN. Your actual buyer won't see it in their GSTR-2B, and some random business gets unexpected ITC. Always verify the GSTIN using a GSTIN Validator before entering.
2. Missing Invoices
Every tax invoice must be in GSTR-1. Missing invoices mean your buyer can't claim ITC. Check your invoice register against GSTR-1 before filing.
3. Wrong Place of Supply
This determines whether the transaction is intra-state (CGST + SGST) or inter-state (IGST). Getting it wrong means wrong tax type — and you'll need to correct it via amendment.
4. Not Reporting Credit Notes
If you issued a credit note against a B2B invoice, it must be reported in Table 9. Otherwise, your buyer's GSTR-2B will show the full invoice amount but no credit note — causing reconciliation issues.
5. Duplicate Invoice Numbers
The portal doesn't block duplicate invoice numbers (for the same GSTIN), but it creates problems during reconciliation. Use a unique, sequential invoice numbering system.
How to File Nil GSTR-1
If you had no outward supplies during the period — no sales, no advances, no credit/debit notes:
- Login → Returns Dashboard → Select period
- Click GSTR-1 → Prepare Online
- Click Generate GSTR-1 Summary → Click File Nil GSTR-1
- Confirm and file with EVC
Nil GSTR-1 can also be filed via SMS to 14409. Format: NIL <GSTIN> <Period> <1>.
Amendments in GSTR-1 — Fixing Errors
Made a mistake in a previous period's GSTR-1? Use the amendment tables in the current period:
- Table 9A: Amend B2B invoices from previous periods
- Table 9C: Amend B2C (large) and export invoices from previous periods
You can amend invoice details like GSTIN, tax rate, and values. But you can't delete an invoice that was already reported — you can only modify it through amendment or issue a credit note.
Time limit for amendments: You can amend GSTR-1 of a period until the 30th November of the year following the financial year to which the invoice belongs.
Late Filing Consequences
| Consequence | Detail | |---|---| | Late fee | ₹50/day (₹20/day for nil), max ₹5,000 per return | | Buyer's ITC blocked | Your invoices won't flow to buyer's GSTR-2B | | GSTR-3B blocked | Can't file GSTR-3B for the next period | | E-way bill blocked | After 2 consecutive months of non-filing | | Compliance rating drops | Affects your GST score and buyer confidence |
Tips for Smooth GSTR-1 Filing
- File before the 11th — Don't wait until the last day. Portal traffic peaks on due dates and the system can be slow.
- Use the JSON upload method for large numbers of invoices — prepare offline using the GSTR-1 offline tool and upload the JSON. Much faster than entering invoices one by one.
- Reconcile with your accounting software — Most accounting packages (Tally, Zoho, ClearTax) have GSTR-1 report generation. Cross-check before filing.
- File GSTR-1 before GSTR-3B — Always. Your summary in GSTR-3B should align with GSTR-1 details.
- Track e-invoice auto-population — If you generate e-invoices, verify that all of them have flowed into GSTR-1 before filing.
Related SmartGST Tools
- GST Calculator — Calculate GST on any invoice
- GSTIN Validator — Verify buyer GSTIN before entering
- HSN Code Finder — Find the right HSN code for Table 12
- Due Date Calendar — Never miss the 11th
- Invoice Generator — Create GST-compliant invoices