USCDI and US Core explained
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SubscribeUpdated April 28, 2026
Healthcare IT is a dynamic environment, and the push for digitization is especially strong in the US, where the ONC Cures Act Final Rule has triggered a steady stream of criteria and deadlines.
There are two key US governmental agencies that enforce the provisions of the ONC Cures Act Final Rule, The Office of the National Coordinator for Health Information Technology (ONC) and Centers for Medicare & Medicaid Services (CMS).
These agencies have worked together to formulate a set of rules primarily focused on matters related to Fast Healthcare Interoperability Resources (FHIR), with a specific emphasis on addressing information-blocking and enhancing interoperability.
ONC Cures Act Final Rule
The ONC Cures Act Final Rule gives patients and authorized healthcare providers secure access to electronic health information (EHI), with key provisions around information blocking, interoperability, API functionality, and certification. The most far-reaching compliance criteria are §170.315(g)(10) — Standardized API for patient and population services, and §170.315(b)(10) — Electronic Health Information export.
The CMS Interoperability and Patient Access Final Rule mandates that health information must be available to patients and their clinicians via APIs, improving prior authorization and care coordination, reducing costs, and putting individuals at the center of their own healthcare.
Much of the regulation is focused on a core data set that care providers must be able to share. This core data set is defined by the ONC as the United States Core Data for Interoperability (USCDI) and is part of the ONC Cures Act Final Rule to set a baseline of required data elements for interoperability.
United States Core Data for Interoperability (USCDI)
USCDI represents the most basic building blocks of healthcare interoperability: a standardized, and actively evolving, set of data elements required for sharing information between health IT systems. These data elements cover a wide range of health information, including patient demographics, clinical notes, medications, allergies, problems, procedures, laboratory results, and imaging reports.
USCDI V1 laid the foundation for interoperability throughout the ONC Cures Act Final Rule. Since then, it has been updated annually. USCDI v5 was published in July 2024, adding 16 new data elements and two new data classes, Observations and Orders. USCDI v6 followed in July 2025, adding a further 6 new data elements, with draft v7 already published in January 2026, proposing 30 additional elements. ONC publishes a draft version each January and a final version each July, keeping the standard in step with clinical, technological, and policy developments.
The current regulatory baseline for certified health IT is USCDI v3, as adopted in the HTI-1 Final Rule. Higher versions can be voluntarily adopted by vendors ahead of regulatory requirements through ONC’s Standards Version Advancement Process (SVAP).
US Core and how it relates to USCDI
The US Core Implementation Guides provide the technical specifications and implementation guidance needed to put USCDI into practice using FHIR. They define the profiles, data elements, and RESTful interactions that health IT systems must support to achieve interoperability, effectively translating USCDI’s “what” into FHIR’s “how.”
USCDI facilitates data exchange; US Core specifies how to achieve it using FHIR. Each new version of US Core aligns with a corresponding version of USCDI. The current published version is US Core v7.0.0 (STU7), which aligns with USCDI v5 and is based on FHIR R4.
Looking ahead, HL7’s US Realm Steering Committee decided in January 2024 that the next major version of US Core will be based on FHIR R6, bypassing R5 entirely for US regulatory purposes. This is a strategically significant decision: it means organizations planning long-term FHIR roadmaps in the US should be aware that the next regulatory baseline will eventually shift to R6, though no timeline has been confirmed yet.
How about USCDI+?
USCDI+ extends the core standard by defining domain- or program-specific data element lists for specialized use cases. ONC is advancing this initiative in the areas of public health and quality measurement. Feedback on USCDI+ datasets is also increasingly being used to inform which data elements are mature enough to graduate into the core USCDI standard, making USCDI+ an important proving ground for future versions of the base specification.
What about TEFCA?
No overview of the US regulatory landscape is complete without mentioning TEFCA, the Trusted Exchange Framework and Common Agreement. While USCDI and US Core define what data must be shared and how it must be structured, TEFCA defines where it flows. It establishes the governance and technical framework for nationwide health data exchange across a “network of networks” built on FHIR APIs.
TEFCA is now in active production, with multiple Qualified Health Information Networks operational and FHIR-based exchange increasingly being rolled out across the framework. For organizations operating in the US, understanding TEFCA alongside USCDI and US Core is essential, they are three interlocking pieces of the same interoperability picture.
Broaden your knowledge on US healthcare regulations
As one of the initiators of FHIR, Firely keeps a close eye on all FHIR-related compliance requirements, and we believe our insights have value for the wider healthcare IT community.
Our US healthcare regulations eBook gives you a practical overview of all the relevant rules, implementation guides, and technologies. It’s a must-read that will help you understand their scope, decide what affects your use case, and help you make decisions.
As ONC and CMS continue to converge regulations and policy towards FHIR, Firely provides the software, training, and expertise that bring the standard to life. We’ve been involved since the beginning, with 100% FHIR-based solutions that enable compliance and innovation in one go. Who better to help you navigate the regulations, meet the deadlines, and make your HealthTech future-proof?
This Health IT Module is 2015 Edition compliant and has been certified by an ONC-ACB in accordance with the applicable certification criteria adopted by the Secretary of Health and Human Services. This certification does not represent an endorsement by the U.S. Department of Health and Human Services.
