If your friend or his father had held the property for more than 3 years, then there will be Long Term Capital Gain. LTCG has to be calculated by deducting from the sale proceeds the indexed cost of acquisition of the property. Capital Gains Tax at 20% on the capital gain (not on the entire sale proceeds) is to be paid. This can be avoided by adopting any of the provisions of Sec. 54 of the I.T. Act, if applicable and available.