How to Fix a Mismatch Between GSTR-1 and GSTR-3B

A GSTR-1 and GSTR-3B mismatch occurs when the outward supplies reported in GSTR-1 do not match the tax liability declared in GSTR-3B for the same tax period. This discrepancy can trigger scrutiny under Rule 88C of the CGST Rules, 2017, leading to a notice in Form GST DRC-01B (Demand and Recovery Certificate) that requires taxpayers to either pay the differential tax or explain the difference within seven days.

Such mismatches commonly arise because GSTR-1 captures invoice-level transaction details, while GSTR-3B is a self-declared summary return used to report and pay Goods and Services Tax (GST) liability. Since the GST portal automatically compares the two returns after filing, even small reporting errors, omissions or timing differences can result in discrepancies that require reconciliation.

How the gap opens between the two returns

A gap between GSTR-1 and GSTR-3B arises when the outward supplies reported in GSTR-1 do not match the tax liability reported in GSTR-3B for the same tax period. Common causes include classification errors, timing differences, duplicate reporting, period mismatches and omissions.

Since July 2025, CBIC has auto-populated the outward liability section of GSTR-3B from filed GSTR-1, GSTR-1A and Invoice Furnishing Facility (IFF) data, and has locked those fields from manual editing. However, mismatches can still occur. Common causes include:

Wrong tax head classification

An interstate sale reported under CGST/SGST instead of IGST. The total tax may be correct, but GSTN treats each tax head separately.

Credit note timing

A credit note issued after GSTR-1 is filed but before GSTR-3B is submitted can create a difference between the reported invoice value and tax liability.

Invoice duplication

The same invoice reported twice in GSTR-1 can inflate outward supply figures relative to the tax paid.

Period-shift payments

Tax paid in the wrong tax period can create a shortfall in one period and an excess payment in another.

Table 3.1 omissions

A supply reported in GSTR-1 but omitted from Table 3.1 of GSTR-3B can create a direct mismatch and may trigger a DRC-01B notice.

Each mismatch requires a specific correction. Differences should be reconciled promptly rather than left for annual return filing.

Rule 88C: What the notice actually triggers

A Rule 88C notice requires the taxpayer to either pay the tax shortfall identified between GSTR-1 and GSTR-3B or explain the difference through Form DRC-01B within seven days. Failure to respond can lead to recovery proceedings and penalties under the CGST Act.

On receiving Form DRC-01B, the registered person has two valid responses:

• Pay the shortfall: Calculate the difference, pay it along with interest at 18% per annum under Section 50 of the CGST Act through Form GST DRC-03, and report the payment in Part B of DRC-01B.
• Contest the gap: Submit an explanation in Part B of DRC-01B on the GST portal, supported by relevant facts and documentation.

The seven-day timeline is mandatory. If no action is taken, or if the explanation is not accepted, recovery proceedings under Section 79 may be initiated. A confirmed demand under Section 73(9) can attract a penalty of 10% of the differential tax or ₹10,000, whichever is higher.

Rule 88C was introduced through Notification No. 26/2022-Central Tax dated 26 December 2022 and applies where the tax liability reported in GSTR-1 exceeds the tax paid through GSTR-3B beyond the prescribed threshold.

A notable exception is the 2024 ruling in M/S LGW Industries Limited vs Union of India, where the Calcutta High Court held that a numerical mismatch between GSTR-1 and GSTR-3B does not, in itself, establish unpaid tax. In certain cases, adjudication under Section 73 or 74 may be required before recovery.

How can a GSTR-1 and GSTR-3B mismatch be corrected?

The correction method depends on whether GSTR-3B for the affected period has already been filed.

Where both returns have already been filed, the correction process generally involves:

1. Identifying the error, such as a wrong tax head, duplicate entry, omitted supply or timing difference.
2. Reporting the correction through the appropriate amendment table in the next GSTR-1, such as Table 4A for B2B invoice amendments, Table 9A for export amendments and Table 9B for credit or debit note amendments.
3. Reflecting the revised tax liability in the corresponding GSTR-3B.
4. Paying any additional tax through DRC-03 along with interest under Section 50, calculated from the original return due date.

Amendments for a financial year can be made up to 30 November of the following financial year or the date of filing GSTR-9, whichever is earlier. For FY 2025–26, the deadline is 30 November 2026.

How can GSTR-1 and GSTR-3B mismatches be prevented?

GSTR-1 and GSTR-3B mismatches can be prevented through timely reconciliation and accurate return filing. The most effective check is to compare Table 4 of GSTR-1 with Table 3.1 of GSTR-3B before filing. Any difference should be identified and documented before submission.

Additional practices that help prevent mismatches include:

• File GSTR-1 before GSTR-3B. Since July 2025, the outward liability fields in GSTR-3B are auto-populated from GSTR-1 and cannot be edited manually.
• Match credit and debit notes to the same filing period as the original invoice wherever possible.
• Verify the IGST and CGST/SGST classification of interstate transactions before filing.
• Ensure the same invoice is not reported in both the B2B and B2C tables, or in multiple returns.

With Rule 88C enforcement and auto-populated GSTR-3B liability fields, unresolved mismatches can lead to notices, recovery proceedings and other compliance risks.

Conclusion

A GSTR-1 and GSTR-3B mismatch is easier and less costly to fix when identified before filing rather than after a DRC-01B notice is issued. Regular reconciliation, timely corrections and accurate reporting can help businesses avoid interest, penalties and recovery proceedings. TallyPrime supports this process with GST reconciliation reports that highlight voucher-level differences early, helping businesses resolve discrepancies before returns are filed.