Section 17(2)(a) in The Khadi And Village Industries Commission Employees (Pension) Regulations, 1984
(a)The authority issuing the order of substantive appointment to a post under the commission as is referred to in sub-regulation (1) shall alongwith such order require in writing the employee of the Commission to exercise the option under that sub-regulation within three months of date of issue of such order, if he is on leave on that day, within 3 months of his return from leave, whichever is later and also bring to his notice to provisions of clause (b).