GST reconciliation errors rarely show up immediately — they surface months later as a mismatch notice, by which point tracing the original error takes far longer than catching it would have during the original filing cycle.
GSTR-2B mismatch: the most common source of trouble
Input tax credit claimed without matching against GSTR-2B is the single most frequent cause of GST notices. Vendors filing late, filing incorrectly, or not filing at all directly affects your available input credit — and this needs monthly reconciliation, not a once-a-year check.
E-way bill and invoice mismatches
- E-way bill values not matching invoice values, often due to timing differences between generation and dispatch
- HSN code inconsistencies across invoices for the same product, which can trigger classification queries
- Round-off and rate discrepancies between what's charged and what's reported
Reverse charge mechanism gaps
Transactions requiring reverse charge treatment are frequently missed entirely, particularly for services from unregistered vendors or specific notified categories. This creates a compliance gap that often isn't caught until an audit specifically looks for it.
Building a reconciliation habit that actually catches issues
A monthly reconciliation checklist — matching GSTR-1, GSTR-2B, GSTR-3B and the books of accounts against each other — catches the majority of these issues while they're still easy to correct, rather than discovering them during a notice response under time pressure.