Final answer:
A health plan must publish star rating information in materials, including the enrollment guide, at least 45 calendar days before the annual enrollment period as required by CMS.
Step-by-step explanation:
According to the Centers for Medicare & Medicaid Services (CMS), a health plan must publish star rating information in its materials, such as the enrollment guide, within 45 calendar days before the start of the annual enrollment period. This is essential as star ratings play a critical role in informing beneficiaries about the quality of the health plans prior to making selections. The star ratings are based on several criteria, including quality of care, plan responsiveness, and customer service, aiming to help consumers compare and choose plans more effectively.