Held that under the matching concept of income and expenditure, the assessee had merely discharged its contractual obligation by making provision for periodic maintenance cost and since accounts were maintained by the assessee on mercantile basis, the provision had to be made by the assessee in its books and accordingly, became an allowable expenditure under section 37(1) under the normal provisions of the Act.  Accordingly, the expenditure attributable to each year has been claimed as deduction both under the normal provisions of the Act as well as in the computation of book profits under section 115JB of the Act. It would not fall under the category of provision made for a contingent liability or unascertained liability. (AY.2013-14 to 2015-16)