Medicare has four parts: Part A for hospital care, Part B for outpatient and physician services, Part C (Medicare Advantage) for plans from private insurers, and Part D for prescription drugs. Each has its own costs, rules, and enrollment timing.
It depends on employer size. If your (or your spouse’s) employer has 20+ employees, that plan usually pays first and you can delay Part B without penalty. If the employer has fewer than 20 employees, Medicare typically pays first, so you generally should enroll in Part B at 65.
When you retire, your active employer coverage usually ends, which triggers an 8-month Special Enrollment Period to sign up for Medicare Part B without penalty. Some employers offer retiree coverage or an HRA that works alongside Medicare.
Part A covers hospital/inpatient care, Part B covers doctors and outpatient care, Part C (Medicare Advantage) is a private all-in-one alternative to A and B, and Part D covers prescription drugs.
Your first chance is the 7-month Initial Enrollment Period around your 65th birthday. After that, the Annual Enrollment Period (Oct 15 to Dec 7) lets you change Medicare Advantage and Part D plans, and Special Enrollment Periods apply after events like leaving employer coverage.