An uncle who earned significant undeclared cash income from real estate between 2000-2008 is being blackmailed with copies of his old tax returns. The discussion confirms that failing to declare income and pay taxes is a crime, and he could face penalties from the Income Tax department. Experts advise consulting a Chartered Accountant to assess the situation, potentially regularise the default through voluntary disclosure or payment of penalties, and to investigate how the blackmailer obtained the return copies. While tax departments generally have powers to reassess older cases, specific rules regarding the timeframe for reopening returns, especially for large amounts of escaped income, should be discussed with the CA.