Simple GSTR-1 Filing for Beginners (Step by Step)

If you are filing GSTR-1 for beginners, here is the core idea: GSTR-1 is the monthly or quarterly return where you report every outward supply (sale) you made, invoice by invoice. You log in to gst.gov.in, enter or auto-import your sales invoices into the right tables, check the summary, and submit. Get your sales data clean first, and the filing itself takes minutes.

What is GSTR-1 and who has to file it?

GSTR-1 is a GST return that reports the details of all your outward supplies of goods and services for a tax period. In plain terms, it is your sales return: every invoice you raised goes here so the government and your buyers can see it.

Every normal GST-registered business must file GSTR-1, whether you sell goods, services, or both. You file even if you had zero sales in the period, by submitting a "Nil" return.

Who does NOT file GSTR-1

• Composition scheme dealers, who file CMP-08 and GSTR-4 instead.
• Input Service Distributors (ISD) and certain TDS/TCS deductors, who have their own returns.

GSTR-1 feeds your buyer's GSTR-2B, which decides the input tax credit (ITC) they can claim. So filing it accurately and on time is not just your problem; your customers depend on it. For the bigger picture, see our complete GSTR-1 filing guide.

Before you start: what you need

Filing goes smoothly only if your data is ready. Gather these before you log in.

• GST login credentials for the portal.
• A list of all sales invoices for the period, with invoice number, date, value, and tax.
• Buyer GSTINs for every B2B sale.
• HSN or SAC codes for your goods and services. If you are unsure, read our HSN and SAC codes guide.
• Credit and debit notes issued during the period.
• Place of supply details, since this decides CGST+SGST (intra-state) versus IGST (inter-state).

Step-by-step: filing your first GSTR-1

1. Log in to gst.gov.in with your username and password.
2. Go to Returns Dashboard, select the financial year and the tax period (month or quarter).
3. Click Prepare Online under GSTR-1 (or use the offline tool / your software to upload a JSON).
4. Enter B2B invoices in the B2B table (4A, 4B). Add each buyer's GSTIN, invoice number, date, taxable value, and tax.
5. Enter B2C sales. Large inter-state B2C invoices above the limit go in B2C (Large) (5A); the rest go as a consolidated, rate-wise summary in B2C (Others) (7).
6. Add credit and debit notes in the CDNR table for registered buyers, CDNUR for unregistered ones.
7. Fill the HSN summary with quantity, value, and tax per HSN/SAC code.
8. Add document series in the Documents Issued table (invoice number ranges used).
9. Click Generate Summary and check the totals against your books.
10. File the return using DSC (digital signature) or EVC (OTP to your registered mobile). Once filed, it cannot be revised; you correct mistakes in a later period.

Note the due dates carefully. As of 2026, monthly filers generally file by the 11th of the next month and quarterly (QRMP) filers by the 13th after the quarter, but these dates can change and sometimes get extended. Confirm the exact date on gst.gov.in or with your CA. See our GSTR-1 due dates and late fees page.

Where your invoice data goes (B2B and B2C tables)

The single most confusing part for beginners is which table an invoice belongs in. The rule is based on who the buyer is.

B2B (business-to-business)

If your buyer is GST-registered and gives you a GSTIN, the invoice is B2B. You report it invoice-by-invoice in the B2B table, with the buyer's GSTIN. This lets them claim ITC.

B2C (business-to-consumer)

If your buyer is an ordinary consumer with no GSTIN, the invoice is B2C. You usually do not list each invoice separately; you report a rate-wise, state-wise summary. The exception is large inter-state B2C invoices, which are listed individually.

If this split confuses you, our explainer on B2B vs B2C invoices under GST walks through it with examples.

A worked example (small trader, realistic ₹)

Say you run Sharma Hardware Stores in Pune, Maharashtra. In April you made these sales:

• Sale 1 (B2B, intra-state): ₹1,00,000 of fittings to Patil Constructions (a registered Maharashtra firm) at 18% GST. Tax = ₹18,000, split as CGST ₹9,000 + SGST ₹9,000. Goes in the B2B table with Patil's GSTIN.
• Sale 2 (B2B, inter-state): ₹50,000 of tools to a registered buyer in Gujarat at 18%. Tax = IGST ₹9,000, because it is inter-state. Goes in the B2B table.
• Sale 3 (B2C): ₹40,000 of mixed counter sales to walk-in customers at 18%. Reported as a consolidated B2C (Others) summary, rate-wise. Tax = ₹7,200 (CGST ₹3,600 + SGST ₹3,600).

Your GSTR-1 for April shows total taxable outward supplies of ₹1,90,000 and total tax of ₹34,200. The B2B lines carry GSTINs; the B2C line is a single summary row. Need to compute the tax split quickly? Use our GST calculator.

Beginner mistakes to avoid

• Wrong tax type: Charging CGST+SGST on an inter-state sale (or IGST on an intra-state one). Always check the place of supply.
• Putting B2B invoices in B2C: This denies your buyer their ITC and invites complaints.
• Wrong GSTIN: A single typo in the buyer's GSTIN breaks their credit. Verify it.
• Forgetting credit/debit notes: These adjust your tax and must be reported.
• Missing the deadline: Late filing means late fees and blocks your buyers' GSTR-2B.
• Confusing GSTR-1 with GSTR-3B: GSTR-1 reports sales detail; GSTR-3B is the summary where you pay tax. See GSTR-1 vs GSTR-3B.

Most of these errors come from messy invoice data, not from the portal. Invodo keeps your invoices GST-correct from the start, assigns the right CGST/SGST/IGST automatically, sorts B2B and B2C, and exports clean GSTR-1 data so your first filing is painless. Start free with Invodo and file with confidence.