ADVISOR’S NOTETAX PARAMARSH DESK
GSTR-1 · OCT 2026 · 5 MIN READ · GST KNOWLEDGE CENTER

What is GSTR-1? Due dates, sections and common errors

Written by Tax Paramarsh editorial teamReviewed by Tax Paramarsh GST deskLast updated 3 October 2026Applies to: GST rules in force on 3 October 2026

GSTR-1 is the return where you report your sales. It matters more than ever: your buyers’ input tax credit comes from it, and since July 2025 your GSTR-3B tax liability is taken straight from it.

GSTTAX PARAMARSH · ADVISOR’S NOTE

What GSTR-1 reports

  • B2B sales — invoice by invoice, with each buyer’s GSTIN.
  • Large inter-state B2C invoices (above ₹1 lakh) — invoice by invoice.
  • Other B2C sales — a summary by tax rate and state.
  • Exports and SEZ supplies, credit and debit notes, an HSN-wise summary and a list of documents issued.

Due dates

  • Monthly filers: the 11th of the next month.
  • QRMP filers (turnover up to ₹5 crore): the 13th of the month after the quarter. For the first two months of a quarter, B2B invoices can be uploaded through the optional IFF by the 13th, so buyers get credit monthly.

Correcting mistakes: GSTR-1A

Errors spotted after filing GSTR-1 can be corrected in GSTR-1A for the same period before you file GSTR-3B. Later corrections go through amendments in a following month.

Errors that cause the most trouble

  • B2B sales reported as B2C — your buyer loses the credit.
  • Wrong buyer GSTIN or invoice reported in the wrong month.
  • Credit notes missing for returns and discounts.
  • Wrong HSN codes or tax rates after the September 2025 rate changes.

Key takeaways

  • GSTR-1 reports your sales; your buyers’ credit depends on it.
  • Due on the 11th (monthly) or the 13th after the quarter (QRMP).
  • Fix errors in GSTR-1A before filing GSTR-3B.

Common questions

What happens if GSTR-1 is filed late?

A late fee applies (₹50 a day, or ₹20 for nil returns, capped by turnover), and your B2B buyers may not see their credit in time.

Is GSTR-1 needed if there were no sales?

Yes — a nil GSTR-1 must still be filed.

Related

RELATED GST SERVICEGST Return FilingRELATED INDUSTRYGST for traders & wholesalersGST TOOLGST Health Check
Need help with this every month?Tax Paramarsh can review your sales, purchases and GST records every month — and file on time.

General information, reviewed on 3 October 2026 — not advice for your specific case. GST rules, forms and due dates change; talk to us before acting.

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MORE NOTES
GSTR-3BHow GSTR-3B works — and why it is now locked to GSTR-1READ →GSTR-2B / ITCWhat is GSTR-2B? How input tax credit reaches youREAD →