5 CFR 870.505: Optional insurance: Waiver/cancellation of insurance.

(a) An insured individual may cancel entirely any type of Optional insurance, or reduce the number of multiples of his/her Option B insurance, at any time by filing a waiver of Optional insurance coverage. An employee files with the employing office. An annuitant files with OPM or other office that administers his/her retirement system. If still employed, a compensationer files with the employing office, and if not still employed, with OPM. Exception: an individual who has assigned his/her insurance under subpart I of this part cannot cancel Option A or Option B coverage.

(b) A cancellation of Optional insurance becomes effective, and Optional insurance stops, at the end of the pay period in which the waiver is properly filed. Exception: if Option C is cancelled because there are no eligible family members, the effective date is retroactive to the end of the pay period in which there stopped being any eligible family members.

(c) A waiver of Optional insurance remains in effect until it is cancelled as provided in § 870.506.