5 C.F.R. § 351.601
Order of release from competitive level
(a) Each agency must select competing employees for release from a competitive level (including release from a competitive level involving a pay band) under this part in the inverse order of retention standing, beginning with the employee with the lowest retention standing on the retention register. An agency may not release a competing employee from a competitive level while retaining in that level an employee with lower retention standing except:
(1) As required under § 351.606 when an employee is retained under a mandatory exception or under § 351.806 when an employee is entitled to a new written notice of reduction in force; or
(2) As permitted under § 351.607 when an employee is retained under a permissive continuing exception or under § 351.608 when an employee is retained under a permissive temporary exception.
(b) At its option an agency may provide for intervening displacement within the competitive level before final release of the employee with the lowest-retention standing from the competitive level.
(c) When competing employees in the same tenure group have identical performance credits as calculated pursuant to § 351.503 (as augmented by veterans' preference as described in § 351.504), are in the same tenure subgroup, and have identical service dates (as calculated pursuant to § 351.505) and are therefore tied for release from a competitive level, the agency may select any tied employee for release.