This bill, titled the Medicare Advantage Supplemental Benefits Transparency Act of 2026, seeks to enhance transparency regarding supplemental benefits provided by Medicare Advantage (MA) plans. It amends the Social Security Act to require MA organizations to submit detailed enrollee-level data on these benefits to the Secretary of Health and Human Services. This data must include eligibility requirements, the applicable benefit category, utilization rates, and payment information, such as the total amount spent per enrollee and out-of-pocket costs. The requirement for data submission will commence with plan years beginning on or after January 1, 2029 . The Secretary is mandated to make this data available for evaluations, analyses, and health care research, and to publish a de-identified public-use data file on the Centers for Medicare & Medicaid Services (CMS) website. Crucially, procedures must be in place to safeguard the privacy and security of any individually identifiable enrollee information, and $12,000,000 is appropriated for the bill's implementation.