Held that the provision made for periodic wearing course overlay expenses on the basis of the report of an independent consultant is an ascertained liability allowable as deduction. Any addition towards provision would enhance the taxable profit which is eligible for deduction under S. 80-IA(4)(i) and would  be a revenue neutral exercise. The  assessee-company is required to maintain surface roughness of the expressway and relay the surface every five years as per the concessionaire agreement between the assessee and NHAI and, therefore, the provision made by the assessee for periodic wearing course overlay expenses on the basis of the report of an independent consultant is an ascertained liability allowable as deduction, more so as the AO has allowed similar claim in other assessment years..(AY.2010-11 to 2015-16)