Common GST Invoice Mistakes That Trigger a Compliance Notice
A GST notice usually isn't a surprise audit — it's an automated flag from a mismatch or an anomaly the system already noticed. Most of the time, the underlying cause is mundane and repeat-offender in nature. Here are the ones worth actually checking for.
The usual suspects
- Gaps or duplicates in invoice numbering — a skipped number (often from a deleted draft or an edited spreadsheet row) or a reused one is exactly what Rule 46(b) exists to prevent, and it's one of the easiest things to check mechanically.
- GSTR-1 and GSTR-3B disagreeing — see GSTR-1 vs GSTR-3B for why this happens and how to prevent it structurally.
- Wrong place of supply leading to a CGST+SGST/IGST mismatch against what your customer's own return shows. See place of supply rules explained.
- Claiming input tax credit against a supplier who hasn't filed their own return — your credit can be reversed even though your invoice was correct, simply because the other side didn't file.
- Wrong or inconsistent HSN/SAC codes across invoices for the same product or service — see HSN and SAC codes explained.
- Charging GST while composition-registered, or the reverse — not charging it when required. See composition scheme vs regular GST.
The pattern behind almost all of them
Nearly every item on this list is a consistency failure, not a knowledge failure — the business usually knows the rule, but the invoice, the return, and the ledger were maintained as three separate records that quietly drifted apart. A GST notice is frequently the first moment anyone notices the drift.
What actually prevents this
The fix isn't more careful manual checking — it's not maintaining three separate records of the same facts in the first place. An invoice, its GST split, and its numbering should come from one source, checked against itself automatically rather than trusted by habit. This is exactly the philosophy behind Settle's own data integrity checks — cross-checking its own numbers rather than assuming they stayed correct.