GSTR-1 vs GSTR-3B: The Difference, the Due Dates, and Why GSTR-3B Is Now Locked to Your GSTR-1

What is the difference between GSTR-1 and GSTR-3B?

GSTR-1 is your sales report. Every invoice you raised in the period goes into it, listed separately, and no tax is paid when you file it. GSTR-3B is your tax return. You enter summary totals, claim the Input Tax Credit that is available in your GSTR-2B, and pay the net GST you owe. GSTR-1 is filed first and GSTR-3B after.

Both are mandatory for every regular GST registered business, including a nil return in a month with no sales.

The part most guides written before mid 2025 still get wrong: you can no longer fix a wrong sales figure by typing over it in GSTR-3B. Since the July 2025 tax period the outward liability in GSTR-3B is auto populated from GSTR-1, GSTR-1A or IFF and is locked. If the number is wrong, you correct it in GSTR-1A before you file GSTR-3B, not afterwards.

GSTR-1 vs GSTR-3B: The Short Answer

Suresh runs a readymade garment shop in Jaipur. Three years of GST registration, a CA who handles the filings, and no reason to think about any of this until a Form DRC-01B notice landed on his portal in February. The message was short. Your GSTR-1 shows a higher tax liability than what you paid in GSTR-3B. Respond within seven days.

His CA was travelling. Seven days on the portal means seven calendar days, not working days. So Suresh did what most shop owners do at that point and searched for the difference between the two forms he had been filing for three years.

That is not a failure on his part. Someone else files, the system runs quietly, and the gap in understanding only shows up when a notice arrives. What follows is the whole thing in plain terms: what each return does, when each is due, what changed in 2025 that most articles have not caught up with, and what actually happens when the two do not match.

The simplest way to hold it in your head: GSTR-1 says here is what I sold. GSTR-3B says here is the tax I owe, take it.

What Is GSTR-1 and What Goes Into It

GSTR-1 is a report of sales, not purchases. That is the first thing people get backwards. Nothing you bought goes into GSTR-1.

Think of it as your official sales diary submitted to the government. Every invoice raised during the period goes in, listed one by one, with the buyer's GSTIN where the buyer is registered.

What goes into GSTR-1:

• B2B invoices, every invoice raised to a GST registered business, with their GSTIN

• B2C sales to unregistered customers, with interstate invoices above Rs 1 lakh reported invoice wise in Table 5 and everything else reported as a consolidated summary

• Export invoices, with or without payment of tax

• Credit notes and debit notes against previously issued invoices

• An HSN summary of what you sold, by HSN or SAC code

• Advances received where payment came in before the supply

On that Rs 1 lakh figure: the threshold for invoice wise reporting of interstate B2C supplies in Table 5 was Rs 2.5 lakh until 31 July 2024. Notification No. 12/2024 Central Tax dated 10 July 2024 amended Rule 59(4) of the CGST Rules and brought it down to Rs 1 lakh with effect from 1 August 2024. A surprising number of guides still print the old number. If you are billing interstate to walk in customers, this is worth checking on your own invoices.

If you want the portal walkthrough for this return rather than the concept, that is on the GSTR-1 filing guide.

No tax is paid when you file GSTR-1. It is purely a reporting exercise. But it does something important for the people you sell to. When you file GSTR-1 and upload your B2B invoices, those invoices appear in your buyer's GSTR-2B, and that is how your buyer gets Input Tax Credit. Delay your GSTR-1 and your buyer's working capital takes the hit, not yours.

What Is GSTR-3B and Where the Tax Gets Paid

GSTR-3B is where money actually moves.

You do not list individual bills here. You enter consolidated totals: total taxable sales, IGST collected, CGST, SGST, total ITC available, ITC claimed, and the net tax payable after adjusting credit. One set of summary figures for the period.

What goes into GSTR-3B:

• Summary of outward taxable supplies, meaning total sales and total tax collected

• Inward supplies liable to reverse charge, where you pay the GST instead of your supplier

• Eligible Input Tax Credit claimed, checked against GSTR-2B

• ITC reversal, for credit that has to go back

• Net tax liability, output tax minus eligible ITC

• Actual payment through the cash ledger or the credit ledger

• Late fee and interest, calculated by the portal itself if you are past the due date

GSTR-3B cannot be filed without paying the tax first. The portal will not accept the return until the liability is cleared. And it cannot be filed at all if the previous period's GSTR-3B is still pending, which is what makes a single missed month so disruptive.

GSTR-1 vs GSTR-3B: The Full Comparison Table

GSTR-1 vs GSTR-2B vs GSTR-3B, and Where GSTR-2 and GSTR-3 Went

Most people searching this topic are actually holding three forms in their head, not two. GSTR-1, GSTR-2B and GSTR-3B is the real working set, because you cannot file GSTR-3B correctly without reading GSTR-2B first.

GSTR-2B is generated for you on the 14th of each month from what your suppliers filed in their GSTR-1. It is static, meaning it does not change after generation. GSTR-2A shows the same underlying data but keeps updating live as suppliers file. For deciding how much ITC to claim in GSTR-3B, GSTR-2B is the reference document, not GSTR-2A.

So what happened to GSTR-2 and GSTR-3? They were part of the original 2017 design and were never brought into force. The plan was a three form loop: GSTR-1 for outward supplies, GSTR-2 where the buyer would accept or reject each of those invoices, and GSTR-3 as the auto compiled final return. GSTR-2 and GSTR-3 were suspended within months because the matching load was unworkable at that scale.

GSTR-3B was introduced as a stopgap summary return so tax collection could continue while the design was reworked. Nine years later the stopgap is still the main return.

What filled the gap:

• GSTR-2A, a live view of your purchase side

• GSTR-2B, the static monthly statement that decides your ITC

• GSTR-1A, which lets you amend a GSTR-1 for the same period before GSTR-3B is filed

• IMS, the Invoice Management System, where the accept and reject idea from the original GSTR-2 has quietly returned

The short answer when someone asks about GSTR-1, 2, 3 and 3B: only GSTR-1 and GSTR-3B are filed. GSTR-2 and GSTR-3 are dead. GSTR-2B and GSTR-1A do the work in between.

Who Needs to File GSTR-3B, and Is GSTR-1 Monthly or Quarterly

Every regular GST registered taxpayer files GSTR-3B. There is no turnover floor and no exemption for a quiet month, because a nil return is still a return.

Who does not file it:

• Composition dealers, who file CMP-08 and an annual return instead. If that is you, the composition scheme guide is the right page.

• Input Service Distributors

• Non resident taxable persons

• Persons deducting TDS or collecting TCS under GST

On frequency, both returns follow the same rule and it is set by turnover:

• Turnover above Rs 5 crore: monthly. GSTR-1 by the 11th, GSTR-3B by the 20th.

• Turnover up to Rs 5 crore: you may opt into QRMP and file both quarterly, while still paying tax monthly through PMT-06.

QRMP is a genuine decision rather than a formality, and it has a catch that most shops miss around the Invoice Furnishing Facility. That is covered in full on the QRMP scheme page.

Which One Do You File First: The Correct Sequence in 2026

The order is not optional and getting it wrong is now more expensive than it used to be.

1. File GSTR-1 first, with every outward supply invoice for the period.

2. Check GSTR-2B on the 14th. The portal generates it from your suppliers' GSTR-1 filings and it shows exactly how much ITC you are eligible to claim.

3. Reconcile GSTR-2B against your own purchase register. If a supplier's invoice is missing, chase them, because you cannot claim it until it appears.

4. If your own GSTR-1 has an error, fix it in GSTR-1A now, before you touch GSTR-3B. This step did not exist in the old workflow and it is the one people skip.

5. File GSTR-3B. The outward figures will already be filled in and locked. Claim only the ITC that GSTR-2B shows, pay, and submit.

Under Section 16(2)(aa) as it is being enforced, provisional ITC is not allowed. Claiming more than GSTR-2B shows triggers a Rule 88D notice in Form DRC-01C, which carries the same seven day response window as DRC-01B.

If you want the step by step portal walkthrough for the last stage, that is on the GSTR-3B filing guide.

GSTR-1 and GSTR-3B Due Dates for FY 2026-27

These are the standard dates. The government does extend deadlines occasionally, so confirm on gst.gov.in before you rely on any of them.

Monthly filers, turnover above Rs 5 crore

QRMP filers, turnover up to Rs 5 crore

The 22nd applies to Category 1 states and the 24th to Category 2 states. Check which category your state falls into on the portal. The PMT-06 dates shown cover the first two months of each quarter, because the third month's tax is paid along with the quarterly GSTR-3B.

Late fee, if you miss any of these: Rs 50 a day for a normal return, split Rs 25 CGST and Rs 25 SGST, capped at Rs 10,000 per return, and Rs 20 a day for a nil return. On GSTR-3B you also owe 18 per cent a year interest on unpaid tax from the original due date. The full picture is on the GST late filing penalty guide.

GSTR-3B Is Now Hard Locked to Your GSTR-1: The Change Most Guides Missed

This is the section that makes almost every older article on this topic out of date, including, until this update, ours.

From the July 2025 tax period, filed in August 2025, the auto populated outward tax liability in GSTR-3B became non editable. GSTN calls it hard locking. The figures flow in from your GSTR-1, your GSTR-1A and, for QRMP filers, your IFF, and the portal will not let you change them.

Before this, those fields were editable purely for convenience. If your GSTR-1 said one thing and you believed the real number was different, you could type over it in GSTR-3B and move on. That single habit is where a very large share of Rule 88C mismatches came from, and it is now closed.

What this means in practice:

• The number in GSTR-1 is the number in GSTR-3B. There is no second chance to adjust it at the payment stage.

• A wrong sales figure has to be corrected upstream, in GSTR-1A, before GSTR-3B for that period is filed.

• Rushing GSTR-1 to hit the 11th and planning to "fix it in 3B" is no longer a strategy that works.

There is a second lock coming. GSTN has indicated that the ITC side, Table 4 of GSTR-3B, is headed the same way, tied to what appears in GSTR-2B and IMS. Timelines on this have moved before, so treat it as expected rather than fixed, and check the portal advisories before you plan around it.

How to Fix a GSTR-1 or GSTR-3B Mistake Now That Editing Is Blocked

Neither return has a revision facility. What changed is the route you take instead.

If the mistake is in GSTR-1 and you have not filed GSTR-3B yet. Use GSTR-1A for the same period. You can add an invoice you forgot or amend one you reported wrongly, and the net effect of GSTR-1 plus GSTR-1A is what auto populates into GSTR-3B. This is the cleanest fix available and it is the one to reach for first.

If the mistake is in GSTR-1 and GSTR-3B is already filed. Use the amendment tables in the following period's GSTR-1. You reference the original invoice and enter the corrected details. The buyer's GSTR-2B updates in the period the amendment is filed, not the original one, so tell them.

If the mistake is on the ITC side of GSTR-3B. The credit fields are still editable, so reverse or claim the difference in the next period's GSTR-3B. If the excess is material, interest may apply. Self correcting before a notice arrives is always the better outcome.

If the mistake is in the outward liability of GSTR-3B. You cannot fix it inside GSTR-3B. The only route is upstream, through GSTR-1A for that period or an amendment in a later GSTR-1.

Every one of these has an outer deadline. Corrections run until the earlier of 30 November following the end of the financial year, or the date you file the annual return for that year.

And there is now a wall behind that. No GST return under Sections 37, 39, 44 or 52 can be filed more than three years after its original due date. That covers GSTR-1, GSTR-3B, GSTR-4, GSTR-5, GSTR-6, GSTR-7, GSTR-8 and GSTR-9, and it took effect from the July 2025 tax period. Past that point the period is permanently blocked on the portal. There is no late fee route, no penalty and file option. It is simply closed. If you have old pending returns sitting somewhere, this is the thing to deal with this month rather than next year. The annual return guide covers the GSTR-9 side of it.

GSTR-1 vs GSTR-3B Mismatch: Rule 88C, Form DRC-01B and the Seven Day Clock

Back to Suresh. His GSTR-1 declared a certain amount of tax on his sales and the GSTR-3B for the same period showed a lower payment. The gap triggered an automated notice with no officer involved anywhere in the process.

Rule 88C was inserted into the CGST Rules in December 2022 and it automated exactly this check. When the tax payable as per GSTR-1 exceeds the tax actually paid in GSTR-3B by a specified amount or percentage, the portal generates Form GST DRC-01B on its own. It appears on your dashboard and goes to your registered email. Part A of the form states the mismatch and the exact difference.

From that moment you have seven calendar days. Two options:

• Pay the difference. Use Form GST DRC-03 to pay the shortfall along with 18 per cent a year interest calculated from the original due date, then record the payment in Part B of DRC-01B.

• Explain it. If the gap has a genuine cause, a timing difference on a credit note, an amendment, a reporting error that did not change the tax actually payable, set it out clearly in Part B with supporting documents.

Do neither and the portal blocks your GSTR-1 filing for subsequent periods under Rule 59(6)(d), and recovery proceedings under Section 79 of the CGST Act become available.

Common causes of a mismatch, in roughly the order we see them:

• The right figure in GSTR-1 entered under the wrong table in GSTR-3B

• Timing differences, typically a credit note issued after GSTR-1 was filed but before GSTR-3B

• The wrong tax head, CGST and SGST paid where the transaction required IGST or the other way round

• Typing errors during manual data entry into a second system

• An amendment to an earlier GSTR-1 that never made it into the corresponding GSTR-3B

• Duplicated invoices in GSTR-1, or invoices missing from one return but present in the other

Seven days is not much when your CA is busy or travelling. If a DRC-01B arrives, forward it the same day. Do not wait for the weekend to pass, because the count does not pause for weekends or holidays.

Why Clean Billing Data Is Now the Whole Game

Look at that list of causes again. Almost every one of them starts in the same place: the sales data was entered once for billing and then entered again, by hand, for the return.

Manual re entry is where mismatches are born. It was survivable when GSTR-3B was editable, because you could reconcile at the payment stage and adjust. Now that the outward liability is locked to GSTR-1, the reconciliation has to happen before GSTR-1 is filed, or it happens through a GSTR-1A correction, or it does not happen and you get a notice.

The practical consequence is that the quality of your billing records now decides the quality of both returns. If your turnover has crossed the e-invoicing threshold, the same logic applies one step earlier, because the IRP data feeds GSTR-1 directly.

That is the problem Accountune is built around. It is a cloud based GST billing, inventory and accounting platform for Indian small businesses, running in Jaipur since 2017. When you raise an invoice in it, that invoice is the source for the GSTR-1 report and the same data feeds the GSTR-3B summary. There is no separate data entry step for returns, so there is no second place for a number to go wrong. You review and submit rather than retype. It runs on a phone, a tablet or a laptop with nothing to install, which matters because it means the owner can look at what is about to be filed rather than hearing about it after a notice. There is a free plan at ₹0 and paid plans start from ₹499 a year.

None of that removes the need to understand what you are filing. A tool makes the numbers consistent. It does not tell you whether the numbers are right. Spend thirty minutes with the two forms once and you will read every notice differently after that.

A last set of habits worth building, whatever you file with:

• File GSTR-1 by the 8th or 9th, not on the 11th. The portal slows down on deadline days and errors happen under time pressure.

• Check GSTR-2B on the 14th, every month, against your purchase register.

• Use GSTR-1A the moment you spot a GSTR-1 error, before GSTR-3B goes in.

• Set four repeating reminders: 8th file GSTR-1, 14th check GSTR-2B, 18th prepare GSTR-3B, 19th file GSTR-3B.

• Deal with any DRC-01B within 24 hours of seeing it, not within seven days.

Suresh's notice was resolved. His CA filed a Part B explanation, the mismatch turned out to be a genuine timing difference on a credit note, and the case closed. The seven days of phone calls in between were avoidable. Not by knowing more law, just by knowing which form does what and where the numbers come from.

If you want your GSTR-1 and GSTR-3B figures to come from the same place, Accountune offers a 4 day free trial with no credit card required.