(4)[ The power to make rules conferred by this section shall include the power to give retrospective effect, from a date not earlier than the date of commencement of this Act, to the rules or any of them and, unless the contrary is permitted (whether expressly or by necessary implication), no retrospective effect shall be given to any rule so as to prejudicially affect the interests of assessees.] [ Inserted by Act 26 of 1974, Section 14 (w.e.f. 18.8.1974).]
