5 CFR 534.403 (a)(3) addresses SES pay and the EX-III pay rate.

(3) Rates of basic pay higher than the rate for level III of the Executive Schedule but less than or equal to the rate for level II of the Executive Schedule generally are reserved for those senior executives who have demonstrated the highest levels of individual performance and/or made the greatest contributions to the agency's performance, as determined by the agency through the administration of its performance appraisal system for senior executives, or, in the case of newly-appointed senior executives, those who possess superior leadership or other competencies, consistent with the agency's strategic human capital plan.