Part A — hospital insurance
Covers inpatient hospital stays, skilled nursing after a hospital stay, hospice, and some home health. Premium-free for most people (you prepaid via payroll taxes). It has deductibles and coinsurance — which supplements and Advantage plans help with.
Part B — medical insurance
Doctors, outpatient care, tests, durable equipment, preventive care. Has a monthly premium (income-adjusted) and, on its own, no cap on your 20% coinsurance — the main reason almost nobody carries Original Medicare bare.
Part C — Medicare Advantage
Private plans that replace how you receive A + B, usually adding drug coverage and extras like dental or vision. Lower premiums, but networks and prior authorizations. County-by-county availability.
Part D — prescription drugs
Standalone drug plans (with Original Medicare/Medigap) or built into most Advantage plans. Every plan has its own formulary — the same drug can differ wildly in cost between plans, which is why we always run your actual prescription list.
Medigap — Medicare Supplements
Standardized lettered plans (G and N are today’s workhorses) that pay the gaps in Original Medicare. Any doctor who takes Medicare, nationwide, no networks. Higher premium, very predictable costs.
Enrollment windows
Initial (around your 65th birthday), Annual (Oct 15 – Dec 7), Medicare Advantage Open (Jan 1 – Mar 31), and Special periods triggered by life events like retiring or moving. Miss-timing is where the lifetime penalties live.
The famous penalties
Part B: +10% of the premium for every 12 months you were late, for life. Part D: +1% per month late, for life. Both fully avoidable with creditable coverage or on-time enrollment — this is the single best reason to ask questions early.
IRMAA — the income surcharge
Higher incomes pay more for Parts B and D, based on your tax return from two years ago. Retiring often means your surcharge is based on income you no longer earn — there’s an appeal form (SSA-44) for exactly that.
