The Income Tax Department launched 'Operation Clean Money' to investigate cash deposits made during demonetisation from November 9 to December 30, 2016, sending emails or SMS to approximately 18 lakh individuals for further information. Recipients must respond only online within 10 days, and failure to do so could result in enforcement actions under the Income Tax Act. The process involves logging into the e-filing portal, verifying cash transaction data, and submitting a response based on the accuracy of the cash deposits reported.