Why the department already knows
The transaction is not a discovery; it was reported. Under Section 285BA read with Rule 114E, a range of institutions must file a Statement of Financial Transactions listing high-value dealings against your PAN. The common triggers for an NRI are a property registration of ₹30 lakh or more, aggregate purchases of shares or mutual funds of ₹10 lakh or more, and large deposits, while dividend and interest are reported with no threshold at all.
That information flows into your Annual Information Statement, which the department matches against your return. Where a big transaction sits in the AIS with no matching return, or no return at all, the system flags it. So the starting point is that the data is real and already held; the question is only whether your tax position on it is correct, which is usually a matter of explanation rather than liability.
How the e-campaign works, and how you answer it
The department surfaces the mismatch through the compliance portal as an e-campaign or e-verification message, run under the e-Verification Scheme. It is not itself a demand or a penalty; it is an opportunity to respond before anything escalates. On the portal you go through each flagged transaction and give feedback: that it is correct, that it is not yours, that it relates to another PAN, that it is a duplicate, or that it needs a corrected return.
Many flags are benign once explained. A property sale where the gain was small after cost, a mutual-fund purchase that was simply an investment and not income, a deposit that was your own transferred funds. Where a return was genuinely due and not filed, or filed wrong, you file or revise it as part of the response. The key is to answer within the window with accurate feedback and, where needed, the corrected filing.
What happens if you ignore it
The reason to deal with an AIS mismatch promptly is what it can become. An unanswered or unsatisfactory response does not simply lapse; the department can carry the same information into a Section 148A inquiry and, from there, a reassessment of the year. At that point you are defending a reopened assessment rather than closing a portal message, which is slower, more formal and more exposed.
For an NRI abroad, the portal message is easy to miss or to distrust as a scam, and that is exactly how a simple mismatch grows. A practising CA reads the AIS, reconciles each flagged transaction against your real tax position, files the portal response and any corrected return, and keeps the matter from ever reaching the reassessment stage, all under your authorisation from the Indian side.