Termination of Employment of Workmen (Special Provisions) Act (No. 45 of 1971) - Sect 18
Service of notices
18. Any notice which is required by this Act to be served on, or given to, any person shall, if it is not served on, or given personally to, such person, be deemed to have been duly served or given-
(a) if it is left at the usual or last known place of abode or business of such person; or
(b) if it is sent to him by post in a registered letter addressed to the usual or last known place of abode or of business of such person.