Held that the assessee was under regulatory regime where tariff was determined in advance by a regulatory commission and fuel and fixed cost adjustments were unbilled revenue determined as per a formula set out in the applicable regulations. These sums would be recovered after the receipt of the order of the commission. Till then, there was uncertainty in the revenue and unbilled revenue was recognised in the statement of profit and loss. The fact that these provisions were not disallowed by the Assessing Officer under the normal provisions of the Act indicated that the Assessing Officer had accepted these provisions as having accrued during the year. Fuel and fixed cost adjustments were unbilled revenue as firmly set out by the commission. The assessee had unbilled income because of these adjustments. The addition was to be deleted.(AY. 2007-08, 2009-10, 2012-13, 2014-15)