(5)[ Where any assessment done under sub-section (2) is contrary to the claim of the importer or exporter [***] [ Inserted by Act 29 of 2006, Section 20 (w.e.f. 13.7.2006).], and in cases other than those where the importer or the exporter, as the case may be, confirms his acceptance of the said assessment in writing, the proper officer shall pass a speaking order within fifteen days from the date of assessment of the bill of entry or the shipping bill, as the case may be.]