Fix GSTR-1 vs GSTR-3B Mismatch (the Excel Method)

Last updated: 27 June 2026 · Reflects the GSTR-3B liability hard-lock (July 2025 onward).

To fix a GSTR-1 vs GSTR-3B mismatch, put both returns' outward-tax figures side by side in Excel — rate-wise for taxable value, IGST, CGST and SGST — subtract one from the other, and trace any non-zero difference to a specific invoice, amendment or timing gap. Since July 2025 the GSTR-3B liability fields are auto-filled from GSTR-1 and locked, so most mismatches now come from amendments, credit notes or wrong-period reporting rather than typing errors.

Key takeaways

GSTR-1 reports invoices; GSTR-3B reports the tax you pay. Their outward-tax totals should agree.
Compare rate-wise, not just on one grand total — offsetting errors can hide in a single figure.
Subtract in Excel (3B − 1) for taxable value and each tax head; a non-zero line points to the problem.
Common causes: credit/debit notes, GSTR-1A amendments, invoices booked in the wrong month, and B2C nettings.
Table 3 of GSTR-3B is now hard-locked (auto-filled from GSTR-1/IFF since July 2025), so you fix the source, not the 3B field.
Mismatches invite notices and can block your buyers' ITC — reconcile every month before filing.

Fact box. GSTR-1 lists outward supplies invoice-wise; GSTR-3B is the summary return where tax is actually paid. From the July 2025 period, GSTR-3B's outward-liability fields (Table 3) are auto-populated from GSTR-1/IFF and non-editable, so the two returns should reconcile by design. (Source: GSTN advisory.)

Why do GSTR-1 and GSTR-3B differ?

In principle they shouldn't — both report the same sales. A gap almost always traces to one of these:

Amendments — an invoice changed via GSTR-1A after 3B was prepared.
Credit/debit notes — recorded in one return's period but not the other.
Wrong-period invoices — a March invoice reported in April's GSTR-1 but taxed in March's 3B (or vice versa).
B2C adjustments — net-offs or amendments to B2C summaries.
Manual 3B entries from before July 2025, now historical.

Because Table 3 of 3B is now locked to the GSTR-1 figure, going forward the usual culprit is timing — the same tax landing in different months.

How do I compare them in Excel?

Pull the rate-wise outward figures from both returns into one grid. Lay out rates down the side and the two returns across:

Rate	Taxable (1)	Taxable (3B)	Diff	IGST (1)	IGST (3B)	Diff
5%	2,00,000	2,00,000	0	…	…	0
18%	8,40,000	8,10,000	30,000	…	…	…
40%	50,000	50,000	0	…	…	0

Put =Taxable_3B - Taxable_1 in the Diff column and copy across every head (IGST, CGST, SGST). Any non-zero cell is your mismatch — and the rate tells you where to look.

Fact box. Always reconcile rate-wise and head-wise, never on a single grand total. Two opposite errors — say one invoice at the wrong rate — can net to zero overall while still being wrong in each slab, which the portal's own checks will catch. (Source: reconciliation good practice.)

How do I trace a specific difference?

Once you know the rate and head, drill into the invoices:

Filter your sales register to that rate and period.
Total taxable value and tax; compare to the GSTR-1 figure for that rate.
Check for credit notes dated in the period that one return included and the other didn't.
Check for invoices with a document date in a different month than when tax was paid.
Confirm any GSTR-1A amendment is reflected in the 3B period.

A quick SUMIFS on the register by rate and month gives you the true figure to compare against both returns.

How do I fix the mismatch?

You fix the source, not the locked 3B field:

If GSTR-1 is wrong, correct it via GSTR-1A (before that period's 3B) or amend in the next GSTR-1.
If an invoice was reported in the wrong month, account for it in the correct period and let the auto-population flow.
If tax was short-paid, pay the difference with interest at 18% p.a. from the due date.
Keep a one-line note of each adjustment so the next month's reconciliation starts clean.

How Ankeshan helps: Ankeshan lines up your GSTR-1 and GSTR-3B figures rate-wise inside Excel, highlights the exact slab and head where they diverge, and links the difference back to the invoices behind it. It's launching soon; join the waitlist.

Frequently asked questions

Why is my GSTR-3B not matching GSTR-1? Usually because of credit notes, amendments, or invoices reported in a different month than the tax was paid. Compare the two rate-wise in Excel to isolate the slab.

Can I edit GSTR-3B if it doesn't match GSTR-1? The outward-liability fields (Table 3) are auto-filled from GSTR-1 and locked since July 2025, so you correct the GSTR-1 source rather than overtyping 3B.

What happens if GSTR-1 and GSTR-3B don't match? Persistent mismatches can trigger notices and may affect your buyers' Input Tax Credit. The portal also runs system checks on the difference.

Does a mismatch attract interest? If the mismatch means you paid tax late or short, interest applies at 18% per annum on the shortfall from the due date.

How often should I reconcile GSTR-1 and 3B? Every month before filing 3B, so any difference is caught while it's small and easy to trace.

Sources

GSTN: GSTR-3B Table 3 auto-population and hard-lock advisory — gst.gov.in.
CBIC: GSTR-1, GSTR-1A and GSTR-3B mechanics; Section 50 interest — cbic-gst.gov.in.

General information, not professional advice. Verify on the official portal for your case. Reviewed by a Chartered Accountant; last updated 27 June 2026.