IN BRIEF

The checks before filing GSTR-3B are the verifications a GST-registered business runs before submitting its monthly summary return — GSTR-1 figures locked, input credit matched to GSTR-2B, blocked credits and reversals removed, reverse charge paid in cash, and set-off made in the prescribed order — so the liability and credit the return locks in are correct.

GSTR-3B looks like the simplest return in GST. Five tables, some auto-filled figures, one payment. That is exactly why it hurts people: the return is short, but it locks in a month of sales, credit and cash, and most of its figures cannot be quietly edited afterwards. The errors that cost money — credit claimed above GSTR-2B, a reversal nobody made, reverse charge paid from credit instead of cash — are all visible before you press submit. You just have to look. Here are the eight looks that matter.

1. File GSTR-1 first — and treat its figures as final

Your outward liability now flows from GSTR-1 into GSTR-3B on its own, and since the July 2025 period it arrives locked: you cannot edit the auto-populated liability inside the 3B. So the sequence matters. File the GSTR-1, read the figures it carries, and if something is wrong, correct it through GSTR-1A before the 3B — that is the door the portal leaves open. Filing the 3B first and hoping to fix the sales side later is how a wrong month becomes a wrong year.

2. Claim ITC up to GSTR-2B — and not one rupee above it

Since January 2022, the law is plain: credit is available only on invoices your supplier has reported and that appear in your GSTR-2B. There is no provisional buffer any more. Claim above the 2B figure and the system itself asks questions — the DRC-01C intimation exists for exactly that gap. If an invoice is in your purchase register but missing from 2B, the answer is to chase the supplier, not to claim and hope.

3. Strip out the blocked credits hiding inside 2B

Presence in GSTR-2B is not the same as eligibility. Motor vehicles, food and beverages, personal-use purchases and the other section 17(5) items routinely appear in 2B because your supplier reported the invoice — the statement does not judge whether you may take the credit. Read the month's credit list once with 17(5) in mind and take the blocked items out yourself, before an assessment does it with interest.

4. Make the month's reversals — all three kinds

First, the 180-day rule: an invoice you have not paid within 180 days takes its credit back, with interest, until you pay it. Second, the supplier-default rule: if your supplier has not filed their own GSTR-3B by 30 September following the financial year, Rule 37A puts their credit on your reversal list. Third, the ordinary ones — goods returned, credit notes received, proportionate reversals where you make exempt supplies too. Reversals reported in the right table, in the right month, are a non-event. Discovered in an audit, they are a demand.

5. Hunt down the reverse-charge liability — and pay it in cash

Reverse charge does not announce itself. It hides in rent paid to an unregistered landlord in the cases the law specifies, in services imported from outside India, in legal fees and goods transport. List the month's inward supplies against the reverse-charge categories, put the liability in the return, and remember the payment rule that catches everyone once: reverse charge is paid in cash. It cannot be set off against input credit — the cash ledger has to carry it. Our note on reverse charge on commercial rent shows how easily this one is missed.

6. Set off the liability in the legal order

When the credit ledgers hold IGST, CGST and SGST balances, the order you burn them in is prescribed, not chosen: IGST credit is exhausted first — against IGST, then CGST, then SGST — before the CGST and SGST credits are touched in their own lanes. Get the order wrong and you pay cash you did not owe while credit sits stranded in the wrong ledger. Thirty seconds of reading the set-off screen saves that.

7. Price the delay honestly if any piece is late

If the month has already slipped — a late GSTR-1, a payment going out after the due date — compute the interest and late fee yourself and provide for them in the return rather than letting the portal's demand arrive later with company. Interest on delayed cash payment runs at 18% a year under section 50. Knowing the number before you file turns a penalty into a cost you chose with open eyes.

8. Before you offset, agree the ledgers with your books

Last, the two-minute habit that catches what the other seven miss: the electronic credit ledger and liability ledger on the portal should agree with the GST ledgers in your books — opening balance, month's movements, closing balance. Where they differ, there is an entry, a claim or a payment one side knows about and the other does not. Find it now, in a month you remember, rather than in the annual reconciliation. And if you are filing a nil return, earn it: no sales, no purchases with credit, no reverse charge — all three, checked, not assumed.

File the 3B after these eight and the return tends to stay filed — no intimations to explain, no credit to defend, no interest to negotiate. The monthly habit also makes the annual GSTR-9 season dramatically shorter, because twelve checked months reconcile themselves.

If your 3B is currently filed on hope and a spreadsheet, our GST returns desk runs this checklist on every client's return before it goes — you are welcome to hand us the month and watch it come back clean.