Chartered Accountant · ICAI M.No. 153926 · FRN 136869W
What each does
GSTR-1 = invoice-level sales detail. GSTR-3B = summary of sales, ITC and tax payable, with the actual payment.
They must match
A mismatch between GSTR-1 and GSTR-3B is a common trigger for department notices, so reconcile them before filing.
Why reconciliation matters in three directions
The two returns must agree with each other and with two more data sets, so reconciliation runs in several directions. First, your GSTR-1 (invoice-level sales) should tie to the sales declared in GSTR-3B; a gap suggests an invoice missed in one return. Second, the input credit you claim in GSTR-3B should match your GSTR-2B, the auto-drafted statement of what suppliers reported. Third, at year-end both should reconcile to your books and, for larger taxpayers, to GSTR-9C. The department’s systems compare GSTR-1 with GSTR-3B automatically, and a persistent mismatch is a common trigger for an ASMT-10 scrutiny notice; large gaps between credit claimed in 3B and available in 2B can even lead to your GSTR-1 filing being blocked under the rules that tie the two together. The practical discipline is to prepare GSTR-1 from the sales register, generate 3B from the same source plus the 2B-matched credit, and reconcile all three before filing rather than after a notice. Catching a missing invoice or an over-claimed credit in the same month it arose is far cheaper than explaining it a year later with interest.