5 C.F.R. § 535.106

A critical position pay rate is considered a rate of basic pay for all purposes, including any applicable premium pay, except—

(a) Application of any saved pay or pay retention provisions (e.g., 5 U.S.C. 5363);

(b) Application of any adverse action provisions (e.g., 5 U.S.C. 7512); or

(c) Application of the General Schedule (GS) pay administration rules in 5 CFR part 531, subpart B; however, a critical position pay rate is treated as a non-GS rate of basic pay in applying the maximum payable rate rule in §§ 531.221 through 531.223 of this chapter, as provided in § 531.221(a)(4).