Which coverage pays first?
When you have Medicare and other health insurance, coordination-of-benefits rules determine the order in which they pay. The coverage that pays first is called the primary payer. Medicare does not always pay first.
Your circumstances matter
Payment order can depend on the kind of other coverage and your circumstances, including employment. The order is not determined by which card you show first or which policy is newest.
Check before making a change
Tell Medicare and your health care providers about other coverage. If you have employer or retiree benefits, ask the benefits administrator how those benefits work with Medicare before changing or dropping them. Use the official guidance for your situation rather than assuming everyone with two cards follows the same rule.
This guide is general education. Your own coverage decisions call for a review of your needs, eligibility, and available options.