Section 8(6)(b) in The Public Liability Insurance Rules, 1991
(b)where the person to be served is an officer serving in Government, if the document is addressed to the person and a copy thereof is endorsed to his Head of the Department and also to the Secretary to the Government, as the case may be, incharge of the Department in which, for the time being, the business relating to the Department, in which the officer is employed, is transacted and is either,-(i)sent by registered post; or(ii)is given or tendered to him;