How to File GST Returns: GSTR-1, IMS and GSTR-3B Step by Step

Which returns does a regular taxpayer file?

A regular GST taxpayer files GSTR-1 for outward supplies and GSTR-3B as the summary return with tax payment, plus an annual return in GSTR-9 if aggregate turnover exceeds ₹2 crore. Taxpayers with turnover up to ₹5 crore can opt for the QRMP scheme, filing GSTR-1 and GSTR-3B quarterly while paying tax monthly through PMT-06 by the 25th. Composition taxpayers file CMP-08 quarterly and GSTR-4 annually instead.

Preparing GSTR-1

Export the sales register and reconcile it with e-invoices (IRNs) and e-way bills. Classify each document correctly: B2B invoices with the buyer's GSTIN, B2C large and small, exports with or without payment, credit and debit notes, advances and HSN summary. Since the GSTR-1 data flows to buyers' GSTR-2B and into your own GSTR-3B, errors spread quickly, so check GSTINs and place of supply before filing.

Reviewing inward supplies in IMS

The Invoice Management System lets you accept, reject or keep pending each invoice uploaded by suppliers. Accepted and deemed-accepted invoices flow into GSTR-2B and form the basis of your input tax credit. Reject invoices that are wrong or duplicated, and keep pending those you are not ready to decide on. Claim ITC only for invoices you have received goods or services against and paid within 180 days.

Filing GSTR-3B

Table 3 liability auto-populates from GSTR-1, GSTR-1A or IFF and has been hard-locked from the July 2025 tax period, so the only way to correct it is GSTR-1A before filing GSTR-3B. Table 4 ITC is populated from GSTR-2B; reverse ineligible credit and Rule 42/43 amounts. Offset liability first against credit in the order the law prescribes, pay the balance in cash, and file with DSC or EVC. Keep working papers for each month.

• Check auto-populated Table 3
• Correct sales errors via GSTR-1A
• Verify Table 4 ITC against GSTR-2B
• Record reversals and ineligible credit
• Offset with ITC and pay cash balance
• File with DSC or EVC and download the acknowledgement

Late filing consequences

Late GSTR-3B attracts a late fee of ₹50 a day (₹20 for nil returns), subject to caps that depend on turnover, plus 18% interest on tax paid late. Non-filing blocks e-way bill generation after two consecutive defaults and can lead to cancellation of registration. Since July 2025, returns cannot be filed after three years from their due date, so a long default becomes permanent.

Records to keep for each return

Assessment and audit can reach back several years, so keep a monthly file for each return period. Store it electronically with a clear folder structure so an officer's query can be answered within days.

• Sales and purchase registers
• GSTR-1, GSTR-3B and GSTR-2B downloads
• IMS action log
• ITC reconciliation and reversal workings
• Challans and cash ledger extracts
• E-invoice and e-way bill reports

Common mistakes

Typical errors are wrong place of supply on inter-state services, B2B invoices reported as B2C, claiming ITC on invoices not in GSTR-2B, ignoring IMS actions and filing GSTR-3B before GSTR-1. Reconcile monthly rather than at year end.

Step by step

1. 1Reconcile sales

   Match the sales register with e-invoices and e-way bills.

2. 2File GSTR-1

   Upload documents and file by the 11th, or IFF/quarterly under QRMP.

3. 3Fix errors

   Use GSTR-1A for corrections before GSTR-3B.

4. 4Act on IMS

   Accept, reject or keep pending supplier invoices.

5. 5Download GSTR-2B

   Reconcile ITC with the purchase register.

6. 6Prepare GSTR-3B

   Verify Table 3 and Table 4; compute reversals.

7. 7Pay tax

   Offset with credit and pay cash balance.

8. 8File GSTR-3B

   File by the due date and save the acknowledgement.