What's the difference between SES, ST, and SL positions?
In an agency covered by the Senior Executive Service (SES), SES positions include positions classified above GS-15 that include duties involving one or more of the functional criteria (executive or managerial) identified in law.
Scientific and professional (ST) positions include positions classified above GS-15 that are not SES positions (i.e., do not involve executive and management responsibilities) and are engaged in research and development in the physical, biological, medical, or engineering sciences, or a closely related field.
Senior level (SL) positions include positions that are not SES positions and are classified above GS-15 based on other factors.
In an agency that is not covered by the SES, either an SL or an ST position may perform duties that involve one or more of the SES functional criteria.