(b)if it considers it desirable or expedient so to do for avoiding genuine hardship in any case or class of cases, by general or special order, authorise any income-tax authority, not being a Joint Commissioner (Appeals) or a Commissioner (Appeals) to admit an application or claim any exemption, deduction, refund or any other relief under this Act after the expiry of the period specified in this Act for making such application or claim and deal with the same on merits as per law;