Complete Guide to GSTR-1 Filing for Indian Businesses in 2025

GSTR-1 is the monthly or quarterly return that every registered GST taxpayer must file to report all outward supplies — that is, every sale or service rendered during the period. Getting GSTR-1 right is critical: errors here affect your buyers' input tax credit and can trigger GST notices.

Who Must File GSTR-1?

Every GST-registered business that makes taxable outward supplies must file GSTR-1. This includes:

• •Regular taxpayers (monthly or quarterly)
• •E-commerce operators
• •SEZ developers and units

Exempt from GSTR-1:

• •Composition scheme dealers (they file CMP-08 and GSTR-4)
• •Input service distributors
• •Non-resident taxable persons

Monthly vs Quarterly Filing

Monthly GSTR-1: Businesses with aggregate annual turnover above ₹5 crore must file monthly. Due date: 11th of the following month.

Quarterly GSTR-1 (QRMP Scheme): Businesses with turnover up to ₹5 crore can opt for quarterly filing. Due date: 13th of the month following the quarter end.

Key Tables in GSTR-1

Understanding what goes where saves hours of confusion:

Table 4: B2B supplies — taxable supplies made to other registered businesses. Include GSTIN, invoice number, date, and HSN code. This is the most important table — your buyer's ITC depends on it.

Table 5: B2C large — supplies above ₹2.5 lakh made to unregistered buyers. Include state-wise breakup.

Table 7: B2C small — all other B2C supplies, summarised state-wise.

Table 9: Amendments to earlier returns — if you made errors in previous months, correct them here.

Table 11: Advance receipts — if you received an advance for future supply.

Table 12: HSN-wise summary — summary of supplies by HSN code.

Common GSTR-1 Mistakes to Avoid

Wrong GSTIN for buyer: Always validate the customer's GSTIN before raising an invoice. A wrong GSTIN means your customer cannot claim ITC on that invoice.

Incorrect HSN code: Use the correct 4-digit or 8-digit HSN code based on your turnover. Wrong HSN codes attract scrutiny during audits.

Missing invoice amendments: If you raised a credit note or corrected an invoice, it must be reported in GSTR-1. Many businesses forget to report amendments.

Ignoring the reconciliation with GSTR-2A: After filing GSTR-1, check that your large B2B buyers see your invoices in their GSTR-2A. If they do not, contact your software vendor — there may be a filing error.

How DaaSu ERP Simplifies GSTR-1

With DaaSu ERP, GSTR-1 preparation is automatic:

• •Every invoice raised is tagged with GST rate, HSN code, and customer GSTIN
• •The system organises invoices into the correct GSTR-1 tables automatically
• •You review the data, make any corrections, and export the JSON file for direct upload to the GST portal
• •DaaSu also alerts you 3 days before the due date so you never file late

Penalty for Late GSTR-1

Late filing attracts a penalty of ₹50 per day (₹25 CGST + ₹25 SGST) for regular taxpayers, and ₹20 per day for NIL returns. More importantly, your buyers cannot claim ITC on your invoices until you file, which can damage business relationships.

File on time. With the right software, it takes 15 minutes every month.