Tax on sale of flat

Only the real owner can sell the flat. If the flat is in your mother's name, then only she can sell it and long term capital gain will come on her. She will have to compute the capital gain and find out how much she is required to invest to save tax. She can either purchase another flat or invest in bonds. Bonds have a lock-in period of 3 years having interest of about 6.5%pa. If a flat is purchased then you can give it on rent. Purchasing flat is cumbersome, take up lot of time and energy, whereas, bonds once invested will be safe for 3 years.