21A notice served under section 29 of the [1952 c. 10.] Income Tax Act 1952 (power to obtain information as to interest paid or credited without deduction of tax) on the Postmaster General before the appointed day shall, if it has not been complied with before that day, be deemed to have been served on the Director of Savings; and subsection (1) of that section shall, in its application on and after that day to the National Savings Bank, have effect as if the reference to interest paid or credited by the Director of Savings included, as regards any period before that day, a reference to interest paid or credited by the Postmaster General to depositors.