my friend who is working jointly his father's business and does not have separate legal income. but he is an active investor in share market from the last 3 years. now today the Notice of Income came : regarding [ transaction of 20k or more in shares for FY 2009-10 , ] his total buy sell never reached more than 1 lac. and eventually he had a loss in share market . that's why he didn't filled the income tax return .