Changes in Estimates :

The percentage of completion method is applied on a cumulative basis in each accounting period to the current estimates of contract revenue and contract costs. Therefore, the effect of a change in the estimate of contract revenue or contract costs, or the effect of a change in the estimate of the outcome of a contract, is accounted for as a change in accounting estimate (see Accounting Standard (AS) 5, Net Profit or Loss for the Period,Prior Period Items and Changes in Accounting Policies). The changed estimates are used in determination of the amount of revenue and expenses  recognised in the statement of profit and loss in the period in which the change is made and in subsequent periods.