How to File GSTR-1 and GSTR-3B for Free (Step-by-Step Guide)

Filing GSTR-1 and GSTR-3B is the monthly (or quarterly) routine that every GST-registered business has to nail. This guide walks through both returns step by step in 2026 - what each one reports, who files when, and how to generate the reports from your invoices for free, so all you have to do on the portal is upload and submit.

GSTR-1 and GSTR-3B at a glance

GSTR-1 is your statement of outward supplies - every sales invoice, credit note and debit note you raised in the period. It feeds your buyers’ input tax credit, so accuracy here directly affects your customers. GSTR-3B is a self-assessed summary return: total outward supplies, input tax credit claimed and net GST payable in cash. This is the return where you actually pay your tax.

• GSTR-1: detailed, invoice-level, no tax payment
• GSTR-3B: summary plus tax payment
• GSTR-1 builds your customer’s ITC; GSTR-3B settles your liability
• Both must reconcile - mismatches trigger notices

Monthly or quarterly? The QRMP rule

Taxpayers with aggregate turnover up to 5 crore can opt into the QRMP scheme - file GSTR-1 and GSTR-3B quarterly while paying tax monthly through a simple challan (PMT-06) for the first two months. Above 5 crore, both returns are monthly. The scheme is optional, so review whether monthly or quarterly works better for your cash flow.

Due dates to remember

In broad terms (always confirm the latest CBIC notification before you file):

• Monthly GSTR-1 - 11th of the next month
• Quarterly GSTR-1 (QRMP) - 13th of the month following the quarter
• Monthly GSTR-3B - 20th, 22nd or 24th of the next month, by state group
• Late filing attracts interest and per-day late fees

Step 1 - Clean your invoice data

A return is only as clean as the invoices behind it. Before generating reports, sanity-check the period:

• Every invoice has a customer, place of supply and state code
• Every taxable item has an HSN/SAC code and the correct GST rate
• Intra-state invoices have CGST + SGST; inter-state have IGST
• Credit and debit notes are linked to the original invoice
• No duplicate or skipped invoice numbers in the financial year

Step 2 - Generate the GSTR-1 report

In Aveon GST, go to Reports > GSTR-1, pick the return period and click Generate. The tool buckets your invoices into the GSTR-1 sections automatically:

• B2B - registered buyers
• B2C (large) - unregistered buyers, invoice over 2.5 lakh, inter-state
• B2C (small) - everything else for unregistered buyers
• Exports and SEZ supplies
• Nil-rated, exempt and non-GST supplies
• Credit and debit notes
• HSN-wise summary

Download the JSON (for portal upload) or Excel (for review with your CA). Numbers below come straight from the invoices you already raised, so there is no second data entry.

Step 3 - Generate the GSTR-3B summary

Once GSTR-1 is in good shape, generate GSTR-3B for the same period. The summary needs:

• Total outward taxable supplies (the GSTR-1 total)
• Inter-state supplies to unregistered persons by state
• Input tax credit (ITC) available, claimed and reversed
• Tax payable and net tax in cash after ITC
• Late fees and interest, if any

In a tool that owns both the sales and purchase ledger, the ITC side comes from your purchase bills and matches what your vendors filed in their GSTR-1 (visible to you as GSTR-2B).

Step 4 - Upload to the GST portal

Log in to www.gst.gov.in. Open Returns Dashboard, pick the period, then GSTR-1 > Prepare Offline > Upload the JSON from your software. Once status is "Processed", review the auto-filled sections, fix any errors, and Submit > File with EVC or DSC. Repeat for GSTR-3B, pay any net tax via the cash ledger, and file.

Reconcile before you hit File

A common notice trigger is mismatch between GSTR-1 (invoice level) and GSTR-3B (summary). Before filing, confirm:

• Total taxable value in GSTR-1 matches the outward supplies in GSTR-3B
• Total CGST + SGST + IGST in GSTR-1 matches GSTR-3B
• ITC claimed in GSTR-3B is supported by GSTR-2B (vendor filings)
• No invoice missed from the period due to a wrong date

Aveon GST generates both returns from the same invoice data, so the totals reconcile by design - no spreadsheet juggling required.