5 C.F.R. § 530.303 – Coverage.

(a) Under 5 U.S.C. 5305, OPM may establish special rates for employees paid under a statutory pay system (as defined in 5 U.S.C. 5302(1)) or any other pay system established by or under Federal statute for civilian positions in the executive branch. Special rates apply only to GS employees unless the approved schedule coverage criteria specifically state otherwise. OPM will establish special rate schedules covering employees under a non-GS pay system only at the request of the agency responsible for administering that system. For employees covered by a non-GS pay system, the responsible agency is subject to the requirements in 5 U.S.C. 5305. To the extent the statutory or regulatory provisions governing the non-GS pay system differ from the regulatory provisions of this subpart, the responsible agency must follow policies that are consistent as possible with this subpart.
(b) An employee's coverage under a special rate schedule is subject to the coverage conditions established by OPM for that schedule, except as provided in paragraph (c) of this section. The coverage conditions for a special rate schedule may be based on occupation, grade, employing agency, geographic location of official worksite, or other factors OPM may determine to be appropriate. An agency determination as to whether an employee meets the coverage conditions for a special rate schedule must be based on the employee's position of record and official worksite. An agency also may be required to consider other employee-specific factors established by OPM to determine special rate coverage, such as special qualifications or certifications.
(c) An agency must pay the applicable special rate to any employee who meets the coverage conditions established by OPM with respect to a special rate schedule unless an authorized agency official determines that a category of employees of the agency will not be covered by a proposed or existing special rate schedule, subject to the following requirements:
1. (1) An authorized agency official may determine that a category of employees of the agency will not be covered by a special rate request or a proposed new special rate schedule. The official must provide written notice to OPM that identifies the specific category or categories of employees who will not be covered by the special rate schedule. The notice must be received by OPM before the effective date of the new special rate schedule.
2. (2) An authorized agency official may remove a category of employees of the agency from coverage under an existing special rate schedule. The official must provide written notice to OPM that identifies the specific category or categories of employees who will not be covered by the special rate schedule. The loss of coverage under a special rate schedule will become effective on the first day of the first pay period beginning on or after the date of the notice to OPM.
(d) An employee covered by a special rate schedule is not entitled to a special rate for any purpose with respect to any period during which the employee is entitled to a higher rate of basic pay under any other legal authority. For example, an employee is not entitled to a special rate if he or she is entitled to a higher locality rate or a retained rate.