Nearly nine lakh registered companies in India are not filing annual tax returns with the Ministry of Corporate Affairs (MCA) and are a potential source of money laundering, Revenue Secretary Hasmukh Adhia said today. Speaking at the Enforcement Day event in New Delhi, Mr Adhia said the task force set up by the Prime Minister's Office is monitoring these companies every 15 days. "There are 15 lakh registered companies... as many as 8-9 lakh are not filing annual returns with the corporate affairs ministry. They have become a potential threat for money laundering," he said.