5 C.F.R. § 550.154 : Administrative Personnel — OFFICE OF PERSONNEL MANAGEMENT — CIVIL SERVICE REGULATIONS — PAY ADMINISTRATION (GENERAL) — PREMIUM PAY —ADMINISTRATIVELY UNCONTROLLABLE WORK — Rates of premium pay payable under 550.151

(a) An agency may pay the premium pay on an annual basis referred to in § 550.151 to an employee who meets the requirements of that section, at one of the following percentages of the employee's rate of basic pay (as defined in § 550.103):
(1) A position which requires an average of at least 3 but not more than 5 hours a week of irregular or occasional overtime work-10 percent;
(2) A position which requires an average of over five but not more than 7 hours a week of irregular or occasional overtime work-15 percent;
(3) A position which requires an average of over seven but not more than 9 hours a week or irregular or occasional overtime work-20 percent;
(4) A position which requires an average of over 9 hours a week of irregular or occasional overtime work-25 percent.
(b) If an agency proposes to pay an employee premium pay on an annual basis under § 550.151 but unusual conditions seem to make the applicable rate in paragraph (a) of this section unsuitable, the agency may propose a rate of premium pay on an annual basis for OPM approval. The proposal shall include full information bearing on the frequency and duration of the irregular or occasional overtime work required; the nature of the work which prevents hours of duty from being controlled administratively; the necessity for the employee being generally responsible for recognizing, without supervision, circumstances which require him to remain on duty; and any other pertinent conditions.
(c) The period of time during which an employee continues to receive premium pay on an annual basis under § 550.151 under the authority of paragraphs (c) or (g) of § 550.162 is not considered in computing the average hours of irregular and occasional overtime work under this section.

5 C.F.R. §550.154

33 FR 12458, 9/4/1968, as amended at 35 FR 6311, 4/18/1970; 55 FR 41178, 10/10/1990; 57 FR 2435, 1/22/1992; 61 FR 3543, 2/1/1996; 67 FR 6641, 2/13/2002