The Designated Employer Representative (DER) is the person an employer identifies to receive drug and alcohol testing communications from service agents (MROs, SAPs, collectors, labs). The DER is responsible for: receiving and acting on test results, authorizing tests, removing employees from safety-sensitive duties when required, and ensuring compliance with the employer drug and alcohol testing program. Under 49 CFR Part 40, the DER must receive results directly from the MRO and must not delegate this responsibility to a service agent. The DER plays a critical role in timely response to positive results, refusals, and violations.