Nearly 70 per cent of the income of political parties in India comes from unknown sources, a decade-long study has found. The study, by Delhi-based think tank Association for Democratic Reforms or ADR, said the Congress saw maximum such incomes, followed by the BJP. Under the Income Tax Act, political parties do not have to pay tax provided they accept all donations above Rs. 20,000 in cheque. While they are required to keep details of donations below Rs 20,000, it has been pointed out that the option of cash donations leaves room for turning black money to white.