Service of notice: authorised methods and deemed receipt rules govern GST communications and legal notification. Section 169 prescribes authorised modes for serving decisions, orders, summonses, notices or other communications-personal delivery (including authorised representatives and employees), registered or speed post or courier with acknowledgement, e mail on record, common portal publication, newspaper publication, and, if impracticable, affixture at last known premises or on the issuing officer's notice board-and provides that service is deemed on the date it is tendered, published or affixed; communications by registered or speed post are deemed received after the normal transit period unless the contrary is proved.