Itr for purchased property using capital gain of earlier sold property

When u have sold the property and capital gains arised then you must have claimed deduction u/s 54 which states that if such capital gain used for purchase of house within 2yrs or constructed within 3 yrs the entire capital gains shall be exempted if cost of such property is more than capital gains arised. now when u have purchased there is no need to show that unless the cost of such property is less than the capital gains arised