Tax definition clarification: surcharge and cess included within tax, extending application to past assessments for compliance purposes. Amendment inserts an Explanation clarifying that for the purposes of clause (a)(ii) of section 40 the term 'tax' includes any surcharge or cess, by whatever name called, and that this inclusive meaning is deemed to have applied retrospectively from the first day of April, 2005, thereby treating surcharge and cess as part of the tax for the sub clause's operation.