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Check GSTR-3B against GSTR-1 and GSTR-2B before you file

After GSTR-3B is filed, the GST portal compares its tax with GSTR-1 and its ITC with GSTR-2B. A gap leads to a DRC-01B or DRC-01C intimation with seven days to reply. Checking the same comparisons before filing, invoice by invoice against your Tally or Busy registers, lets you fix the figures instead of explaining them later.

Run a pre-filing check with CATools →Free during early access · files are not saved

The two comparisons the portal makes

Liability · leads to DRC-01B (Rule 88C)
Tax payable as declared in GSTR-1 or IFF, against tax payable in GSTR-3B, for the same return period.
ITC · leads to DRC-01C (Rule 88D)
ITC claimed in GSTR-3B, against ITC available in GSTR-2B, for the same return period.
Time to respond to either
Seven days to pay or explain. An unanswered intimation blocks the next GSTR-1 or IFF.
The portal shows
Only totals per tax head. Which invoices make up the gap is for you to find.

How to check GSTR-3B before filing, step by step

  1. 1

    File GSTR-1 and wait for GSTR-2B

    The liability check compares against the GSTR-1 you have filed for the month, and the ITC check against the GSTR-2B generated for it. For monthly filers that means after GSTR-1 is filed and GSTR-2B is available, and before GSTR-3B is filed.

  2. 2

    Download the portal files

    GSTR-1 for the month as JSON, and GSTR-2B as JSON or Excel. Add the previous month’s GSTR-2B too, so invoices that appeared there and were booked late are recognised.

  3. 3

    Export the registers from your books

    The sales register and the purchase register for the same month, from Tally, Busy or your own Excel. The columns do not need renaming.

  4. 4

    Take the draft GSTR-3B figures

    Tax payable by head (IGST, CGST, SGST, cess), ITC you are about to claim by head, and the reverse-charge ITC included in it.

  5. 5

    Compare invoice by invoice

    Liability: is every taxable invoice in GSTR-1 also in your GSTR-3B figures? ITC: is every invoice you are claiming in GSTR-2B? Match on GSTIN and invoice number, then compare the taxable value and each tax head, including credit and debit notes.

  6. 6

    Fix what should be fixed, note the rest

    Some differences mean the GSTR-3B figures are wrong: tax left out, or ITC claimed for invoices not yet in GSTR-2B. Correct those before filing. Others are legitimate, such as reverse-charge ITC or tax paid earlier on an advance. Keep a note of the invoices behind them in case an intimation comes.

  7. 7

    File GSTR-3B

    With the corrected figures. The difference left over should be only what you can explain, line by line.

Illustrative example · not a real taxpayer

Example: September GSTR-3B, checked before filing

Draft GSTR-3B figures compared with the filed GSTR-1 and the GSTR-2B for September, after matching both registers invoice by invoice:

Liability: GSTR-1 vs draft GSTR-3B

Tax in GSTR-1 ₹2,16,000 · tax in draft GSTR-3B ₹1,98,000 · difference ₹18,000

  • Sales invoices reported in GSTR-1 but left out when the GSTR-3B figures were prepared

    ₹15,000Fix before filing

  • Advance received in an earlier month, tax already paid in that month’s GSTR-3B; invoice reported in GSTR-1 now

    ₹3,000Explainable

  • Total = difference

    ₹18,000

    Fix ₹15,000 · Explainable ₹3,000

ITC: draft GSTR-3B vs GSTR-2B

ITC in draft GSTR-3B ₹4,86,000 · ITC available in GSTR-2B ₹3,90,000 · difference ₹96,000

  • Purchase invoices in the books that are not in this month’s GSTR-2B (supplier has not filed yet)

    ₹75,000Fix before filing

  • Reverse-charge ITC on services from an unregistered supplier (tax paid in cash; not in GSTR-2B)

    ₹18,000Explainable

  • Invoice in an earlier month’s GSTR-2B, booked late and claimed now

    ₹6,000Explainable

  • Invoice in GSTR-2B but not in the books (reduces the gap)

    −₹3,000Explainable

  • Total = difference

    ₹96,000

    Fix ₹75,000 · Explainable ₹21,000

Illustrative figures for a fictional business, shown as totals across tax heads for readability; the check itself works head by head. “Fix before filing” and “Explainable” are suggestions: what to change in GSTR-3B is the Chartered Accountant’s decision. After the two fixes here, GSTR-3B would show ₹2,13,000 tax and ₹4,11,000 ITC, leaving gaps of ₹3,000 and ₹21,000 that can be explained.

Frequently asked questions

Why check GSTR-3B before filing?

After GSTR-3B is filed, the portal compares it with GSTR-1 and GSTR-2B. A liability gap beyond the set limit leads to a DRC-01B intimation (Rule 88C), and excess ITC to a DRC-01C (Rule 88D). Each gives seven days to pay or explain, and an unanswered one blocks the next GSTR-1 or IFF. Finding the gap before filing lets you correct it instead of replying to it.

What exactly does the portal compare?

For DRC-01B, the tax payable as declared in GSTR-1 or IFF against the tax payable in GSTR-3B for the same return period. For DRC-01C, the ITC claimed in GSTR-3B against the ITC available in GSTR-2B.

How big a difference triggers an intimation?

Both rules apply above an amount and percentage recommended by the GST Council. GSTN describes these as predefined limits; this page does not quote a figure. The pre-filing check shows every difference and leaves the judgement to you.

Can I claim ITC for an invoice that is not in GSTR-2B?

Under section 16(2)(aa) of the CGST Act, ITC is available only when the supplier has furnished the invoice and it has been communicated to you, which is what GSTR-2B shows. Reverse-charge ITC is claimed on the tax you paid, so the amount has to be determined separately. GSTR-2B may include certain reverse-charge supplies, but it does not give the figure claimed in Table 4(A)(2)/(3) of GSTR-3B. Invoices that are simply not there yet are normally claimed in the month they appear.

Which files does the CATools pre-filing check need?

For the liability check: GSTR-1 (JSON from the portal) and the sales register. For the ITC check: GSTR-2B (JSON or Excel) and the purchase register. Registers can come from Tally, Busy or your own Excel, with any column names. You type the draft GSTR-3B figures. Either check can run on its own.

Are my files saved, and do you need my GST portal login?

Neither. The files are read for that one check and not kept, and CATools never asks for the GST portal password. You download the files and file GSTR-3B yourself.

What if a notice comes anyway?

The same matching drafts the reply. Upload the DRC-01B or DRC-01C with the same files, and CATools places every rupee of the difference on a line and drafts the Part B reply with an invoice annexure.

Find the gap before the portal does

Upload GSTR-1, GSTR-2B and your registers, type the draft GSTR-3B figures, and see every difference on a line, invoice by invoice. Nothing is saved.

Run a pre-filing check with CATools →

Already have a notice? Reply to a DRC-01C or a DRC-01B.

Sources

Last reviewed 2 November 2026. This page explains the rules in general terms. It is not legal advice; what to change before filing is for the Chartered Accountant to decide.