Dismissing the appeal of the revenue the Court held that the assessee was following the mercantile system of accounting and in accordance with the notes to the accounts, the assessee was following completed contract method of accounting for contracts. The method of assessment had been accepted by the Department in the past and therefore, in view of the law laid down by the Supreme Court in CIT v.  Bilahari Investments Pvt. Ltd ( 2008) 299 ITR 1 (SC) the Commissioner (Appeals) and the Tribunal had rightly held that there was no justification on the part of the Assessing Officer to change the earlier method adopted by the assessee and to determine the income on estimate basis.( AY.1997-98)