5 CFR § 531.222 - Rates of basic pay that may be used as the highest previous rate.
(a)
(1) Subject to the conditions in this section and § 531.223, the highest previous rate used in applying § 531.221 is—
(i) The highest rate of basic pay previously received by an individual while employed in a civilian position in any part of the Federal Government (including service with the government of the District of Columbia for employees first employed by that government before October 1, 1987), without regard to whether the position was in the GS pay system; or
(ii) The highest rate of basic pay in effect when a GS employee held his or her highest GS grade and highest step within that grade.
(2) The highest previous rate must be a rate of basic pay received by an employee while serving on a regular tour of duty—
(i) Under an appointment not limited to 90 days or less; or
(ii) For a continuous period of not less than 90 days under one or more appointments without a break in service.
(b) For periods of service as a GS employee, the highest previous rate may not be a special rate, except as provided in paragraph (c) of this section. If the highest previous rate is a locality rate, the underlying GS rate or an LEO special base rate associated with that locality rate must be used as the highest previous rate in applying § 531.221(b).
(c) An agency may use a GS employee's special rate established under 5 U.S.C. 5305 and 5 CFR part 530, subpart C, or 38 U.S.C. 7455 as the highest previous rate when all of the following conditions apply:
(1) The employee is reassigned to another position in the same agency at the same grade level;
(2) The special rate is the employee's rate of basic pay immediately before the reassignment; and
(3) An authorized agency official finds that the need for the services of the employee, and the employee's contribution to the program of the agency, will be greater in the position to which reassigned. An agency must make such determinations on a case-by-case basis. In each case, the agency must document the determination to use the special rate as an employee's highest previous rate in writing.
(d) When an agency is barred from using a special rate established under 5 U.S.C. 5305 and 5 CFR part 530, subpart C, or 38 U.S.C. 7455 as an employee's highest previous rate under § 531.223(g), the agency must consider a special rate employee's underlying GS rate (or LEO special base rate, if applicable) in determining the employee's highest previous rate for the purpose of applying paragraph (b) of this section.