Service of notices expanded to include Commissioner approved courier services alongside registered post, effective on assent. Amendment expands permitted methods of service in clause (a) of section 153 by substituting the phrase limiting service to registered post addressed to the addressee or agent with wording permitting service by 'registered post or by such courier as may be approved by the Commissioner of Customs,' thereby authorising approved courier delivery as an alternative method; the amendment takes effect from the date the Bill receives the President's assent.