GSTR-1 vs GSTR-3B: What's the Difference and Which One Do You File First?

Most GST-registered businesses file both GSTR-1 and GSTR-3B every month. Many have been doing it for years. But ask them what the actual difference is - what each return does, why both exist, which one affects their buyers - and you get a blank stare.

That confusion costs money. File in the wrong order, and your buyers lose ITC. Miss GSTR-1 and your GSTR-3B numbers may not match. Get either one wrong and the reconciliation notices start arriving.

Both returns are mandatory. Neither is optional. And the filing order matters.

What is GSTR-1?

GSTR-1 is your outward supply return. Every invoice you issued that month - to registered buyers, unregistered buyers, export shipments, credit notes, debit notes - goes into GSTR-1.

GSTR-1 is an information return. You are not paying any tax through it. You are telling the government: here are all my sales, here is who I sold to, here is the GST I charged.

This matters because GSTR-1 data feeds directly into your buyers' GSTR-2B. When you file GSTR-1 on time with correct invoice details, the GST charged on those invoices shows up in your customer's GSTR-2B automatically. They can then claim that amount as Input Tax Credit.

Delay GSTR-1 and your buyers cannot see the ITC. They either skip claiming it that month or claim it with a mismatch - both create problems.

Who files GSTR-1: all regular GST-registered taxpayers. Composition dealers file CMP-08 instead.

GSTR-1 due dates:

 

What is GSTR-3B?

GSTR-3B is your summary return and your tax payment return. This is where you declare your total GST liability for the month, offset it with ITC, and pay the balance in cash.

GSTR-3B is where the money moves. No tax gets deposited to the government unless you file GSTR-3B and make the payment.

GSTR-1 has invoice-level detail. GSTR-3B works at summary level - you enter total outward supply, total ITC available, and net tax payable. The portal calculates your dues.

Who files GSTR-3B: all regular GST-registered taxpayers. Composition dealers file CMP-08.

GSTR-3B due dates:

 

GSTR-1 vs GSTR-3B: comparison

 

Which one do you file first?

GSTR-1 first. Always.

GSTR-1 is due on the 11th. GSTR-3B is due on the 20th. That 9-day gap exists because GSTR-2B - which your buyers use to verify ITC - generates from GSTR-1 data. Your suppliers need to file their GSTR-1 before the 14th so your GSTR-2B populates in time for you to verify it before your GSTR-3B deadline on the 20th.

The sequence:

Suppliers file GSTR-1 (by 11th) → GSTR-2B auto-generates (14th) → You verify ITC → You file GSTR-3B (by 20th)

Reverse that and you are filing GSTR-3B blind - without knowing what ITC your suppliers have actually reported. You either under-claim and overpay tax, or over-claim and face scrutiny later.

How are the two returns connected?

The two returns are supposed to match. They often do not, and that mismatch is what triggers notices.

The tax on outward supplies you report in GSTR-1 should match what you declare in GSTR-3B Table 3.1. If GSTR-3B shows lower tax than GSTR-1, the system flags it as a possible underpayment.

The ITC you claim in GSTR-3B should match what is available in your GSTR-2B. Claiming ITC on an invoice your supplier has not filed in their GSTR-1 creates a mismatch. Under Rule 36(4), you can claim a maximum of 105% of the ITC reflected in GSTR-2B - anything beyond that gets reversed with interest.

One more thing worth knowing: since 2021, GSTR-3B is partly auto-populated from GSTR-1 data. Outward supply figures from your GSTR-1 feed into GSTR-3B Table 3.1 automatically. This does not mean you skip reviewing it. Auto-population carries forward errors just as reliably as it carries forward correct figures.

Mistakes that create problems

Filing GSTR-3B before GSTR-1 is the most common one. Some businesses deposit tax first and treat GSTR-1 as an afterthought. The tax payment clears, but GSTR-1 filed after the 11th means your buyers' GSTR-2B for that month either did not populate or populated incorrectly. They may have already filed their GSTR-3B without your invoices. That creates ITC mismatches on their side, and they come to you to sort it out.

Wrong figures in GSTR-3B happen more than people admit. GSTR-3B is a summary return, so there is room for arithmetic errors. A common one: entering taxable value instead of tax amount in the liability columns. Another: claiming ITC on exempted supplies. These do not show up immediately - they surface during annual reconciliation or scrutiny.

Filing nil GSTR-1 when there were actual sales is a surprisingly frequent error. If you had no invoices to issue, nil is correct. But businesses occasionally file nil GSTR-1 by mistake when they did have sales, then correctly file GSTR-3B with a tax liability. The mismatch between zero GSTR-1 and non-zero GSTR-3B liability triggers an automatic flag.

Missing B2C or export invoices in GSTR-1. B2B invoices get most of the attention because they affect buyers' ITC. B2C invoices - sales to unregistered buyers - still need to be reported correctly in GSTR-1. Consolidated for sales under ₹2.5 lakh, invoice-level for sales above it.

The QRMP scheme: different rules for smaller taxpayers

If your annual turnover is under ₹5 crore, you may be on the QRMP (Quarterly Return Monthly Payment) scheme. Under QRMP:

• GSTR-1 is filed quarterly (due 13th after quarter end)

• GSTR-3B is filed quarterly (due 22nd or 24th after quarter end)

 

This changes the sequence. For the first two months of a quarter, you are paying tax via PMT-06 without filing a full GSTR-3B. At quarter end, you reconcile everything and file both GSTR-1 and GSTR-3B together.

If you are on QRMP and not sure about your monthly payment obligations, ask your CA. The late fee structure for missed PMT-06 payments is the same as regular GSTR-3B.

What happens when GSTR-1 and GSTR-3B do not match

The GST department runs automated matching. If your GSTR-1 outward supply is consistently higher than what you declared in GSTR-3B - meaning the tax you charged buyers exceeds what you paid - you will receive a notice under Section 61 or an ASMT-10.

The notice gives you a window to explain the difference or pay the shortfall. Acceptable reasons include credit notes reducing net liability, or an error in GSTR-1 that needs amendment in the next month.

What you cannot do is ignore it. A large, unexplained gap between GSTR-1 and GSTR-3B is one of the most common triggers for GST audit selection.

How corrections work

Neither GSTR-1 nor GSTR-3B can be revised after filing.

For GSTR-1 errors - wrong GSTIN, wrong invoice amount, wrong tax rate - corrections go into the following month's GSTR-1 using Table 9A for B2B amendments or Table 9B/9C for others. The corrected data flows into your buyer's GSTR-2B for that subsequent month.

For GSTR-3B, you cannot amend it directly. If you under-declared tax liability, pay the difference with interest via DRC-03. If you over-declared and overpaid, the excess sits in your Electronic Cash Ledger and offsets future payments.

GSTR-1 errors are fixable in the next cycle. GSTR-3B errors cost you interest.

Frequently asked questions

Q1. If I file GSTR-1 but forget GSTR-3B, is my return considered filed? No. They are two separate returns. Filing one does not satisfy the obligation for the other. Late fees apply to each independently.

Q2. Can my buyer claim ITC if I have filed GSTR-3B but not GSTR-1? No. ITC flows from GSTR-1, not GSTR-3B. Your buyer's GSTR-2B only reflects invoices you reported in GSTR-1. GSTR-3B has no impact on their ITC claim.

Q3. What if my GSTR-1 turnover is different from GSTR-3B because of credit notes? Credit notes reduce your net taxable turnover and tax liability. If your GSTR-3B shows lower liability than GSTR-1 because of credit notes, make sure those credit notes are also correctly reported in GSTR-1. The system should reconcile, but keep documentation.

Q4. Can I file GSTR-3B without GSTR-1? The portal allows it. Not recommended. Without GSTR-1 data, your GSTR-3B figures are unverified and your buyers' ITC is blocked.

Q5. Both returns show the same turnover. Does that mean they are correct? Matching numbers are a good sign, not a guarantee. The figures can both be wrong in the same direction. Check against your books, not just between the two returns.