When someone starts receiving more money in their bank account then it is gonna some raise some flags to the tax regulatory body irrespective of the country that is why p2p should not limit to certain extend and for higher limints then the user need to have other source of cashflow that should matches the amount we trade so we can report it as part of the same source too. And it can be done in many ways which I am not denying but there will always be risk associaed with it when we try to evade taxes,  more scrutiny also possible from the banking side and demand source of funds when they think something is off.