Nobody gets a GST notice because they made one massive error. Most notices come from small recurring mismatches that accumulated over several quarters — things you would have caught if you'd looked at the right report once a month.
I've seen businesses panic over notices for discrepancies under ₹10,000. The amount doesn't matter. The Department's system flags mismatches automatically. Once flagged, you have to respond, explain, and document everything. That takes time and money regardless of the amount.
Here's what creates most of these mismatches.
Your supplier filed late or with the wrong GSTIN
This is probably the most common one. Your supplier is slow to file their GSTR-1. You wait. You claim the ITC anyway because you have the invoice and you paid GST on it. Then the mismatch shows up because GSTR-2B doesn't have a matching entry.
The fix is straightforward — use GSTR-2B as your actual ITC reference, not your purchase register. GSTR-2B is the static snapshot the Department uses. If something isn't in GSTR-2B for that month, don't claim it. Wait until it shows up.
Also check: does the invoice you received have your correct GSTIN? Even one transposed digit means the credit lands in someone else's GSTR-2A, not yours.
ITC on things you can't actually claim
Section 17(5) of the CGST Act lists purchases where ITC is blocked entirely. Food and beverages, membership fees, health insurance for employees (unless mandated by law), and motor vehicles used for personal transport are common ones people miss.
It's easy to put a restaurant bill through as "business expense" and claim the ITC. Easy, and incorrect. Build a simple rule into your expense process: before any purchase goes through, confirm it isn't on the blocked list.
The 180-day payment trap
You received an invoice in November. You claimed the ITC. You still haven't paid the supplier by May. That's more than 180 days. Under GST rules, you now have to reverse the ITC and pay interest on it.
Most people only discover this when they're preparing returns and someone asks why the payables ledger has invoices from six months ago. By then it's already a compliance issue.
A simple fix: run an outstanding payables report every month. Any invoice older than 150 days should trigger immediate action — pay it, or flag it for reversal.
Treating month-end as the starting point for reconciliation
If you only start reconciling GSTR-2B against your purchase register the week before filing, you will miss things. Suppliers who haven't filed yet can't be followed up in time. Errors in supplier filings sit unresolved. You either skip valid ITC or claim ITC you can't defend.
Do the comparison mid-month. Download GSTR-2B around the 14th. Match it line by line against your purchase register. Anything missing goes on a follow-up list immediately. By filing time, most issues are already resolved.
Credit notes recorded in the wrong period
When a supplier issues a credit note, your ITC for that month changes. When you issue a credit note to a customer, your output tax changes. If you record these in a different period than they were issued, both sides of the equation end up in different GSTR filings.
The rule is simple: record credit notes in the same month they're issued. No carry-forwards "for convenience."
Thirty minutes of monthly reconciliation work prevents hours of notice response work later. That's the whole case for doing it properly.
