I don't believe that entire money in foreign banks is black. Now business is intrnational. Firms may receive payment from overseas customrs in foreign countries and deposit there. I remember that recently Kejriwal said in a public meeting that ambanis have account in Swiss bank. Then Ambai retorted that he and their firm have several accounts in other countries but the bank account given by Kejriwal is fake. Apart from businessmen in export and import, there are many NRIs who stay in other countries as well as in India. They have genuine accounts in India as well as abroad. My own nephews also have job in Dubai and other countries. Naturally, they have account there but these are genuine and not for black money. I agree that most of black money is in India in form of real estate, gold and jewelery. There is lot of black money in film industry as well.
Black money is generated in two ways. One is that honestly earned but tax is evaded. Another is that when business itself is illegal.
Income Tax department should deal with first one. The police and judiciary have to deal with the second one.
There is another aspect. Businessmen and others use black money for making unlawful payments. Now suppose that you have twenty lakh Rs. black money and you spent most of thsi in payment of dowry and bribe to the government departments, there will be no black money left. Many maintain some sort of ratio between black and white. Say- black money should be twenty percent of the white.
Apart from real estate, film industry, unbilled trade etc , huge amounts of black money is used during elections by all parties especially the two bigger parties. In the five years such money is generated and then used during elections. If elections become clean a lot of black money will stop being generated. i feel that the quantum of black money within country is far higher than outside.