A GSTR-1 vs GSTR-3B mismatch is a difference between the tax you declared on outward supplies in GSTR-1 and the tax you paid through GSTR-3B for the same period. From the July 2025 tax period, the outward liability in GSTR-3B is auto-populated from GSTR-1, GSTR-1A and IFF and cannot be edited, so for current months the two returns now agree by design.
The mismatch did not disappear. It moved. Errors now sit between your books and GSTR-1, in reverse-charge and other tables that stay editable, and in older periods that the department compares in GSTR-9 and scrutiny. Any gap above the portal threshold still triggers a DRC-01B under Rule 88C.
Point | Position |
|---|---|
GSTR-1 | Statement of outward supplies, filed by the 11th (monthly) or 13th after the quarter (QRMP) |
GSTR-3B | Summary return in which tax is paid |
Hard lock | Auto-populated outward liability in GSTR-3B non-editable from the July 2025 tax period (GSTN advisory dated 07-06-2025) |
Correction before filing GSTR-3B | GSTR-1A for the same period |
Intimation for a gap | Form DRC-01B under Rule 88C, inserted by Notification No. 26/2022-Central Tax, dated 26-12-2022 |
Time to respond | 7 days: pay through DRC-03 or explain in Part B |
If you ignore it | GSTR-1 for later periods is blocked under Rule 59(6) |
The difference between GSTR-1 and GSTR-3B
GSTR-1 is the invoice-level statement of what you sold; GSTR-3B is the summary return in which you pay the tax and claim input tax credit. One feeds your buyers' GSTR-2B, the other settles your cash.
Point | GSTR-1 | GSTR-3B |
|---|---|---|
Purpose | Reports every outward supply, invoice by invoice or as B2C summaries | Declares tax payable, ITC claimed and tax paid |
Due date, monthly filers | 11th of the next month | 20th of the next month |
Who uses the data | Your buyers' GSTR-2B and your own GSTR-3B | The department's ledger of tax paid |
Can it be corrected | GSTR-1A before GSTR-3B, or amendments later | Liability locked to GSTR-1 from July 2025 |
Filing order | Must be filed first (Section 39(10)) | Cannot be filed until GSTR-1 for the period is filed |
Because GSTR-3B now copies GSTR-1, the mistake you make in GSTR-1 on the 11th is the tax you pay on the 20th.
What changed with GSTR-3B hard-locking in July 2025
Until mid-2025 you could overwrite the liability that GSTR-1 pushed into GSTR-3B. According to the GSTN advisory of 7 June 2025, from the July 2025 tax period that auto-populated liability is final, and Table 3.2 inter-State supplies to unregistered buyers became non-editable from the same period.
The practical effect is simple. If GSTR-1 is wrong, GSTR-3B will be wrong too, and the only fix before payment is GSTR-1A. Reverse-charge liability is not auto-populated from GSTR-1, so that line still needs manual entry and still causes gaps.
Why GSTR-1 and GSTR-3B still do not match
For periods from July 2025, a mismatch usually means the auto-populated figure was changed by something outside GSTR-1. For earlier periods, the old causes still sit in your history and surface in GSTR-9 and departmental scrutiny.
Cause | Periods affected | What it looks like |
|---|---|---|
Liability overwritten in GSTR-3B before the lock | Up to June 2025 | GSTR-3B lower than GSTR-1 for specific months |
Credit note in GSTR-1 of a later month, already adjusted in an earlier GSTR-3B | Any | One month short, the next month excess |
Amendments in a later GSTR-1 for an earlier invoice | Any | Annual totals match, monthly totals do not |
Reverse-charge tax missed or doubled | Any | Gap in the RCM line only |
Sales missed in GSTR-1 and paid only in GSTR-3B | Up to June 2025 | GSTR-3B higher than GSTR-1 |
Wrong place of supply on B2C orders | Any | Totals match, IGST versus CGST/SGST split does not |
For marketplace sellers, the last row is the commonest. The order goes to the customer's State, and the place of supply must follow it; billing every order as intra-State to your own State shifts tax into the wrong head even when the total is right.
How DRC-01B works under Rule 88C
DRC-01B is an automated intimation sent when the liability in GSTR-1 exceeds the tax paid in GSTR-3B beyond the threshold the portal applies. Part A states the difference; Part B is where you respond.
Rule 88C gives you 7 days to do one of two things: pay the difference with interest through Form DRC-03, or explain in Part B why the difference is not payable. If you do neither, Rule 59(6) blocks GSTR-1 for the next period, and because GSTR-3B cannot be filed without GSTR-1, your whole filing cycle stops.
Never ignore a DRC-01B because you think it is wrong. A one-line explanation with the correct reason clears the block; silence does not.
How to fix a GSTR-1 vs GSTR-3B mismatch step by step
Work from the source data outward, so the fix holds for the annual return as well:
Pull GSTR-1, GSTR-1A and GSTR-3B for every month of the year into one sheet, tax head by tax head.
Mark each month where the two differ and note the direction of the gap.
Match the month's GSTR-1 against your sales register and the marketplace sales reports.
Identify the cause from the table above for each gap.
For the current period, correct GSTR-1 through GSTR-1A before filing GSTR-3B.
For a past period where tax was short-paid, pay the difference with interest through DRC-03.
For a past period where GSTR-3B carried more tax than GSTR-1, record the reason; you cannot adjust it by under-reporting later.
Keep the working sheet; it supports both a DRC-01B reply and Table 9 of GSTR-9.
Interest on short payment runs at 18% a year under Section 50 from the day after the due date. Our guide to GST late fee and interest shows the calculation.
When to use GSTR-1A
GSTR-1A is an optional form for adding or correcting records of a tax period after you file GSTR-1, but before you file that period's GSTR-3B. It is the only way to change the hard-locked liability for the current month.
Use it for missed invoices, a wrong taxable value, a wrong rate or a wrong place of supply in the same period. Once GSTR-3B is filed, the window for that month closes, and later corrections go through amendment tables in a subsequent GSTR-1. Our guide on filing GSTR-3B explains where each table pulls its numbers from.
Where the mismatch starts for e-commerce sellers
For a marketplace seller, GSTR-1 is only as good as the sales data fed into it. The marketplace's tax report, your own invoices and the operator's GSTR-8 are three versions of the same sales, and they rarely agree to the rupee without work.
At Complylocal, the mismatch we trace most often in seller accounts is a monthly GSTR-1 built from the marketplace's order report rather than its tax report. The order report shows orders placed; the tax report shows invoices raised, returns and the place of supply. Building GSTR-1 from orders front-loads sales that are later cancelled and leaves the returns for a credit-note scramble at year end.
Reconcile the tax report against the TCS shown in the operator's GSTR-8 before you file GSTR-1, as part of your monthly GST reconciliation.
What a mismatch costs if it reaches scrutiny
Short payment found later costs the tax, 18% interest and, if the officer issues a show cause notice, a penalty under Section 73 or 74. A DRC-01B left unanswered adds a blocked GSTR-1 to that list.
Situation | Cost |
|---|---|
Short payment found and paid through DRC-03 | Tax plus 18% interest |
DRC-01B not answered within 7 days | GSTR-1 for later periods blocked |
Gap raised in scrutiny or audit | Tax, interest and penalty under Section 73 or 74 |
If a notice has already arrived for an older year, get help replying to GST notices before the reply date, with the monthly working sheet ready.
How to stop GSTR-1 and GSTR-3B mismatches at source
Prevention now means getting GSTR-1 right, because GSTR-3B simply copies it. Three habits do most of the work.
File GSTR-1 from the marketplace tax report and your own invoice register, never from order or settlement reports. Post credit notes in the month of the return, not at year end. Before filing GSTR-3B each month, compare its auto-populated tax with your books and use GSTR-1A if anything is off.
Our overview of GST return types shows how GSTR-1, GSTR-1A, GSTR-3B and GSTR-9 connect.
Want GSTR-1 and GSTR-3B checked against your books before every filing? Talk to Ankush's team about GST return filing.
