Section 17(3) in The Central Government General Pool Residential Accommodation Rules, 2017
(3)If an allottee occupying a lower type of accommodation refuses to accept the offer of an accommodation of the type for which he is eligible under these rules, he shall be permitted to continue in the previously allotted accommodation:Provided that such allottee shall not be eligible for another allotment for a period of six months from the date of non-acceptance of such allotment.
