A Practice Note summarizing group health plan cost-related information that plans and health insurers must disclose to the public in machine-readable files (MRFs) that are updated each month. The cost transparency disclosures reflect a statutory requirement added under the Affordable Care Act (ACA) in 2010 and implemented in tri-agency final regulations issued in November 2020. Under the final regulations, the public disclosures must reflect negotiated rates for covered items and services between the plan or insurer and in-network health providers. Plans or insurers must make additional public disclosures, including billed charges and historical payments, regarding out-of-network providers. Cost-related information for prescription drugs also must be disclosed.