The  assessee made provision for mark to market loss on trading in derivative instruments.Assessing Officer disallowed the said loss holding that mark to market loss at best could be an unascertained liability or a provision for loss which might or might not incur at time of settlement of contract at future date.  Commissioner (Appeals) deleted the addition. The Tribunal held that even though loss was not finally crystallized as per prudent and regular system of accounting, loss had to be accounted for and, thus, same should be allowed. (AY. 2012-13)