Final answer:
The Office of the National Coordinator for Health Information Technology (ONC) is the agency that certifies EHR software systems and providers, as it is authorized to set criteria and certify EHR technologies.
Step-by-step explanation:
The regulatory agency responsible for certifying Electronic Health Record (EHR) software systems and the providers who use them is the Office of the National Coordinator for Health Information Technology (ONC). The ONC is part of the Department of Health and Human Services (HHS) and was established under the Health Information Technology for Economic and Clinical Health (HITECH) Act. It is authorized to establish certification criteria for EHR technology and to certify that particular software meets these standards. Unlike the Center for Devices and Radiological Health (CDRH), which is a branch of the FDA that oversees medical devices, the ONC specifically deals with the certification of health information technology, including EHR systems.