GSTR-1 vs GSTR-3B: What Each Return Actually Does

Two returns, two jobs

GSTR-1 is the invoice-level report of everything you sold — due by the 11th of the following month for monthly filers. It doesn't pay any tax; it publishes your sales detail, which is what your B2B customers' input tax credit depends on.

GSTR-3B is the summary self-declaration where tax actually gets paid — total sales, ITC claimed, net liability — due by the 20th. It's the financial event; GSTR-1 is the data event.

Why mismatches trigger notices

The department reconciles the two automatically. GSTR-1 showing more sales than 3B looks like under-paid tax; the reverse looks like inflated customer credits. Marketplace sellers add a third stream — the platform's reported figures — and three-way mismatches are among the most common notice triggers for e-commerce businesses.

The fix is boring and effective: reconcile books, GSTR-1, and 3B before filing, every month, rather than explaining differences after a notice.

Practical rhythm that works

Close the books by the 7th, file GSTR-1 by the 11th, reconcile ITC against GSTR-2B when it generates, pay and file 3B by the 20th with a buffer day. Businesses that hold this rhythm essentially never see reconciliation notices; businesses that file both at the deadline from different data sources eventually do.