Held that for the purposes of section 42, the terms of the agreement shall prevail for allowing deduction of expenses specified in the agreement. The option to claim expenses incurred prior to the date of commercial production in ten instalments was available only in K block, and not in the C block. According to the production sharing contracts in the C block, expenditure incurred prior to the commercial production shall be aggregated and the loss so assessed as well as loss, if any, incurred in the assessment year relevant to the year in which commercial production commences or in any subsequent assessment year shall be carried forward to succeeding assessment years for being set off as provided in the Income-tax Act. Accordingly, in the absence of any clause for allowing expenses in instalments in C block, the Assessing Officer was not justified in restricting the deduction to 10 per cent. of expenses claimed by the assessee. The Commissioner (Appeals) is  justified in directing the Assessing Officer to allow entire expenses claimed in the C block. That in respect of the K block, the Commissioner (Appeals) had given a categorical finding that all the expenses claimed by the assessee had been incurred post commercial production. According to the production sharing contracts of the K block, the option to claim expenses in instalments was available to the expenses incurred prior to the date of commercial production. Since, the expenses in question were post commercial production expenses, the clause would not apply. Accordingly, the Commissioner (Appeals) is  justified in directing the Assessing Officer to allow the entire expenses claimed in the K block. (AY.2017-18, 2018-19)