Section 169 of the CGST Act
Section 169 of the CGST Act: Service of notice in certain circumstances—
(1) Any decision, order, summons, notice or other communication under this Act or the rules made thereunder shall be served by any one of the following methods, namely:—
(a) by giving or tendering it directly or by a messenger including a courier to the addressee or the taxable person or to his manager or authorised representative or an advocate or a tax practitioner holding authority to appear in the proceedings on behalf of the taxable person or to a person regularly employed by him in connection with the business, or to any adult member of family residing with the taxable person; or
(b) by registered post or speed post or courier with acknowledgement due, to the person for whom it is intended or his authorised representative, if any, at his last known place of business or residence; or
(c) by sending a communication to his e-mail address provided at the time of registration or as amended from time to time; or
(d) by making it available on the common portal; or
(e) by publication in a newspaper circulating in the locality in which the taxable person or the person to whom it is issued is last known to have resided, carried on business or personally worked for gain; or
(f) if none of the modes aforesaid is practicable, by affixing it in some conspicuous place at his last known place of business or residence and if such mode is not practicable for any reason, then by affixing a copy thereof on the notice board of the office of the concerned officer or authority who or which passed such decision or order or issued such summons or notice.
(2) Every decision, order, summons, notice or any communication shall be deemed to have been served on the date on which it is tendered or published or a copy thereof is affixed in the manner provided in sub-section (1).
(3) When such decision, order, summons, notice or any communication is sent by registered post or speed post, it shall be deemed to have been received by the addressee at the expiry of the period normally taken by such post in transit unless the contrary is proved.