Section 15(2)(b) in All India Services (Death-Cum-Retirement Benefits) Rules, 1958
(b)If a member of the Service has been declared by the Medical Board to be completely and permanently incapacitated for further service leave or any extension of leave may be granted to him after the report of the Medical Board has been received, provided that the amount of leave so granted, together with any period of duty beyond the date on which the Medical Board signed their report, shall not exceed 6 months.