GSTR-3B Explained Simply: Tax, ITC and Due Dates in One Place

GSTR-3B is the return where you pay GST. In one short form you declare the tax on your sales, subtract the input tax credit on your purchases, and pay the balance. Monthly filers file by the 20th of the next month. Quarterly filers file by the 22nd or 24th, depending on the State.

What is GSTR-3B, and why does it exist?

Your GSTR-1 tells the government what you sold, invoice by invoice. It collects no money. GSTR-3B is the companion that does: a summary return where you assess your own tax for the period and pay it. Every regular registered business files it, including in a period with no sales and no purchases.

For a small business it is the return that decides how much cash leaves the bank each month.

What do the main tables ask for?

ITC is the GST you paid on purchases, which you set off against the GST on your sales. GSTR-2B is the monthly statement the portal builds from your suppliers' GSTR-1. It is the list of credit you may claim.

When is it due?

If you file monthly, the 20th of the next month. If you are in the QRMP scheme (quarterly returns with monthly payment, open up to Rs 5 crore turnover), the date depends on where your principal place of business is.

The tax itself must be paid by the same date.

What do QRMP filers do in the other two months?

You pay, but you do not file. For the first and second month of each quarter you deposit tax through challan PMT-06 by the 25th of the next month. You have two ways to work out the amount.

• Fixed sum. The portal generates a challan for 35% of the cash you paid in the last quarter's GSTR-3B. Pay it by the 25th and no interest is charged for that month, even if your real tax was higher.
• Self-assessment. You work out the month's sales and credit and pay the actual balance. If you fall short, interest applies on the shortfall.

No challan is needed in a month with no liability, or when the balance in your cash and credit ledgers already covers it.

What does a delay cost?

Interest: 18% a year under section 50, counted from the day after the due date. When you declare the tax in a GSTR-3B filed late, interest is charged only on the part paid in cash, not on the part paid from credit.

Late fee: Rs 50 a day (Rs 25 CGST plus Rs 25 SGST), or Rs 20 a day when no tax is payable. Since June 2021 it is capped for each return: Rs 500 when the tax payable is nil, Rs 2,000 for turnover up to Rs 1.5 crore, Rs 5,000 above that and up to Rs 5 crore, and Rs 10,000 above Rs 5 crore.

Delay has a chain effect too. You cannot file a GSTR-3B while an earlier one is pending, and none can be filed after three years from its due date.

A worked example

You sell furniture within your State and file monthly. Your turnover last year was Rs 90 lakh. In October 2026:

• Sales: Rs 5,00,000 at 18%. Tax on sales: Rs 90,000 (Rs 45,000 CGST and Rs 45,000 SGST).
• Credit in GSTR-2B: Rs 60,000.
• Balance to pay in cash: Rs 30,000.

The return is due on 20 November. You file and pay on 30 November, 10 days late.

• Interest: Rs 30,000 x 18% x 10/365 = Rs 148.
• Late fee: 10 x Rs 50 = Rs 500.
• Extra cost: Rs 648.

Interest runs on Rs 30,000, not Rs 90,000. Over a longer delay the late fee stops at Rs 2,000, but interest keeps running.

What is filled in for you, and what is locked?

Once your GSTR-1 is filed and GSTR-2B is generated, the portal fills Tables 3.1, 3.2 and 4 for you. For years you could overwrite any of it. That has changed for the sales side.

• Sales figures (Tables 3.1 and 3.2). GSTN announced in June 2025 that the liability filled in from GSTR-1, GSTR-1A or IFF would stop being editable from the July 2025 return. A further advisory dated 5 December 2025 applied the same to Table 3.2 from the November 2025 return. As of November 2026, treat these figures as locked.
• Credit (Table 4). Filled from GSTR-2B and still editable, with a warning if you claim more than the statement shows.
• Interest (Table 5.1). Computed by the portal. Reports of a January 2026 advisory say it can be raised but not lowered.

One caution: the portal's own FAQ page still describes the sales figures as editable with a red warning. If a sales figure looks wrong, correct it in GSTR-1A before you file, and the right figure will flow in.

Can you revise a filed GSTR-3B?

No. There is no revised GSTR-3B. Section 39(9) lets you correct an omission or error in the return of a later month or quarter, with interest where tax was short.

• Tax paid short: add the missed sale through a GSTR-1 amendment so that it flows into a later GSTR-3B, or pay at once through Form DRC-03, the voluntary payment form. Interest runs till the day you pay.
• Tax paid in excess: reduce it in a later period through a credit note or amendment in GSTR-1.
• Credit missed: claim it in a later GSTR-3B.

All three close on 30 November after the end of the financial year, or on the day you file your annual return if that is earlier. For FY 2025-26 that is 30 November 2026. What is left after that is settled in the annual return. See who must file GSTR-9.

The mistake people usually make

They claim credit from their purchase bills instead of from GSTR-2B. If a supplier has not filed, that invoice is not in your GSTR-2B, and the credit is not yours to take yet. Claim it anyway and you may have to reverse it later with interest. Open GSTR-2B first, match it to your purchase register, and chase the suppliers who are missing.

Can you file it yourself? With steady sales and a handful of suppliers, yes. If your credit is large or your suppliers file irregularly, a monthly check by a tax expert pays for itself.

Frequently asked questions

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