GSTR-1 is the GST return in which you report your outward supplies — essentially, your sales — for a tax period. The data you file here flows into your customers’ GSTR-2B, which is what lets them claim input tax credit on what they bought from you. That makes GSTR-1 not just your compliance, but theirs too: accurate, on-time filing keeps your buyers happy and your business relationships clean.
Who has to file GSTR-1?
Every business registered under regular GST must file GSTR-1, even in a period with no sales — in which case you file a nil return. Composition scheme taxpayers do not file GSTR-1; they have their own return. Casual taxable persons and a few other categories have separate rules.
How often you file depends on turnover and your chosen scheme. Taxpayers under the Quarterly Return Monthly Payment (QRMP) scheme file GSTR-1 quarterly, while others file monthly.
Due dates: 11th monthly, 13th for QRMP
For monthly filers, GSTR-1 is generally due on the 11th of the month following the tax period. For QRMP (quarterly) filers, the quarterly GSTR-1 is generally due on the 13th of the month following the quarter. QRMP taxpayers can optionally use the Invoice Furnishing Facility (IFF) to upload B2B invoices in the first two months of a quarter so their buyers can claim credit sooner.
Always confirm the current due date on the GST portal before filing, as the government occasionally extends deadlines.
What data goes into GSTR-1
GSTR-1 is organised into tables by the type of supply. The main pieces are:
- B2B supplies — sales to other GST-registered businesses, reported invoice-by-invoice with the buyer’s GSTIN.
- B2C supplies — sales to unregistered consumers, reported as a summary (with large inter-state B2C invoices itemised separately).
- Credit and debit notes issued against earlier invoices.
- Exports and any zero-rated supplies.
- Advances received and adjusted, where applicable.
- An HSN-wise summary of the goods and services supplied during the period.
B2B vs B2C — why the distinction matters
The split between B2B and B2C is central to GSTR-1. B2B invoices must carry the recipient’s GSTIN and are reported individually, because each one feeds your buyer’s input tax credit. B2C invoices are to end consumers who cannot claim credit, so most are reported in summary — though large inter-state B2C invoices (above the prescribed value threshold) are reported at invoice level. Getting a B2B customer’s GSTIN wrong, or filing their invoice as B2C, denies them their credit and usually triggers a phone call.
The HSN summary
GSTR-1 requires an HSN-wise summary of supplies — quantity, value and tax grouped by HSN (for goods) or SAC (for services) code. The number of digits you must report depends on your turnover, with higher-turnover businesses required to report at finer detail. Keeping correct HSN codes on your item masters from the start makes this summary automatic instead of a month-end scramble.
Common mistakes to avoid
- Wrong or missing buyer GSTIN on B2B invoices — this blocks your customer’s input tax credit.
- Misclassifying inter-state supplies as intra-state (or vice versa), which puts tax under the wrong head.
- Forgetting to report credit and debit notes, so your figures do not reconcile with GSTR-3B.
- Skipping or under-reporting the HSN summary.
- Filing late — late fees and interest add up, and your buyers’ credit is delayed.
- Treating a no-sales period as “nothing to do” instead of filing a nil return.
Reconcile before you file
Before submitting, reconcile your GSTR-1 totals with your books and with the values you will report in GSTR-3B. The taxable value and tax in both returns should tell the same story. Accounting software that prepares the GSTR-1 summary directly from your invoices removes most manual re-keying — and most of the errors that come with it. LekhaPro, for example, assembles the B2B, B2C, notes and HSN summary from your posted invoices so the figures match your ledger.