Most GST notices trace back to a small handful of avoidable mistakes. After reviewing hundreds of filings, here are the five we see most often — and exactly how to prevent each one.

1. Claiming Input Tax Credit Before It Appears in GSTR-2B

Since the introduction of GSTR-2B, input tax credit can only be claimed once a supplier's invoice reflects in your auto-drafted statement. Claiming credit based on an invoice alone — before the supplier files their own return — is one of the fastest ways to trigger a mismatch notice.

The fix: reconcile your purchase register against GSTR-2B every month before filing GSTR-3B, not after.

2. Treating "No Sales" as "No Filing Required"

A month with zero transactions still requires a nil return. Businesses that skip filing during a quiet month often don't realise the late fee clock is running until it has already added up.

Why this catches people off guard

Unlike income tax, GST has no informal "below threshold, skip it" exception for registered businesses — registration itself creates the filing obligation, active or not.

3. Misclassifying Goods Under the Wrong HSN Code

An incorrect HSN code can apply the wrong tax rate without anyone noticing until an audit. Cross-check your product classifications annually, especially after any rate notification.

4. Missing the Annual ITC Reconciliation Deadline

Input tax credit for a financial year must be claimed by 30 November of the following year, or with your annual return — whichever is earlier. Credits missed by this date are gone for good.

5. Ignoring Reverse Charge Liability

Payments to unregistered vendors, certain imports, and specified services attract reverse charge — meaning you, not your supplier, owe the tax. This is one of the most commonly overlooked liabilities in GST compliance.

A reconciled GSTR-2B before every filing catches four of these five mistakes automatically — it is the single highest-leverage habit in GST compliance.

If any of this sounds familiar, our GST Return Filing service builds exactly this reconciliation into every monthly cycle — see how it works.