No night pay may be paid when credit hours are earned. That is because when employees earn credit hours, they are not performing regularly scheduled work. By contrast, night pay is authorized for work performed at night during an employees regularly scheduled tour of duty. See 5 U.S.C. 5545(a).
No night pay may be paid for credit hours that are used at night to be absent from the employees basic tour of duty. This is because under 5 U.S.C. 5545(a) and OPM regulations, employees must generally perform work at night to earn night pay. There is no provision of law or OPM regulations that permits night pay to be paid when credit hours are used to be absent from regularly scheduled nightwork.
For requirements on entitlement to night differential when credit hours are earned by wage (prevailing rate) employees and employees employed under title 38, United States Code, see 5 U.S.C. 6123(c)(2).