(a) The sum of pay for nonovertime hours that are part of a firefighter's regular tour of duty (as computed under § 550.1303) and the straight-time portion of overtime pay for hours in a firefighter's regular tour of duty is treated as basic pay only for the following purposes:

(1) Retirement deductions and benefits under chapters 83 and 84 of title 5, United States Code;

(2) Life insurance premiums and benefits under chapter 87 of title 5, United States Code;

(3) Severance pay under section 5595 of title 5, United States Code;

(4) Cost-of-living allowances and post differentials under section 5941 of title 5, United States Code; and

(5) Advances in pay under section 5524a of title 5, United States Code.

(b) The straight-time portion of overtime pay for hours in a firefighter's regular tour of duty is derived by multiplying the applicable firefighter hourly rate of basic pay computed under § 550.1303(a) and (b)(2) by the number of overtime hours in the firefighter's regular tour of duty.

(c) Pay for any nonovertime hours outside a firefighter's regular tour of duty is computed using the firefighter hourly rate of basic pay as provided in § 550.1303(a) and (b)(2), but that pay is not considered basic pay for any purpose, except in applying §§ 550.105 and 550.106.

(d) For firefighters compensated under § 550.1303(b), pay for nonovertime hours within the regular tour of duty, but outside the basic 40-hour workweek, is basic pay only for the purposes listed in paragraph (a) of this section and for the purpose of applying § 410.402(b)(6) of this chapter and §§ 550.105 and 550.106.

(e) Locality pay under 5 U.S.C. 5304 is basic pay for firefighters only to the extent provided in this subpart, § 531.610 of this chapter, or other specific provision of law.