S. 48 : Capital gains-Computation-Cost of acquisition-Indexation cost-Joint Development agreement-Accounting treatment in books of account cannot determine the taxability under income-tax Act-Indexed cost of acquisition-Indexation was allowed till the taxable event of capital gains and not till the date of entering in to development agreement with developer-Provision of section 45(2) cannot be applicable to the assessee who is not a developer. [S 45, 45(2), 145]