The Medicare Enrollment Checklist
Medicare enrollment is the rare government process where missing a deadline costs money for life. This page is the checklist that keeps the family from paying the late-enrollment penalties: the windows, the parts in order, and the three dates that matter.
three windows, one calendar
The Medicare enrollment timeline
Missed windows cost money for life. The three dates on one line: the birthday window, the special period, and the annual open enrollment.
- Birthday window7 months around 65Three months before, the month of, three months after. Part B and Part D live here.
- Special periodWhen coverage endsIf employer coverage continued past 65, the special window opens when it ends, with no penalty.
- Annual enrollmentOct 15 - Dec 7The yearly window for Part D and Advantage changes, starting January 1.
- Every yearMark it on the calendarThe lifetime penalties are avoidable with one calendar reminder, per the savings guide.
Not benefits advice. Medicare rules change and individual situations vary. The Medicare.gov pages and a SHIP counselor (free, local) are the authorities. This page is the family's calendar checklist.
The parts, in order
- Part A (hospital) is usually free if the parent or spouse worked long enough; enrolling on time matters when it is not free.
- Part B (medical) has a premium and a late-enrollment penalty that grows the longer enrollment waits past the deadline.
- Part D (drugs) has its own penalty for late enrollment, even if the parent takes no medicines now. The Medicare explained guide covers each part.
- Supplement or Advantage: the Advantage versus Medigap guide is the decision reference, and its enrollment has its own windows.
The three dates that matter
- The birthday or 65th-birthday month window: enrollment opens three months before the month the parent turns 65 and closes three months after, a seven-month window.
- The special enrollment period: if the parent (or spouse) keeps employer coverage past 65, a special window opens when that coverage ends, avoiding the penalty.
- The annual open enrollment (October 15 to December 7): the yearly window to change Part D or switch between Advantage and Medigap, with changes starting January 1.
The penalties the family can avoid with a calendar
The Part B penalty adds 10 percent of the premium for each full 12-month period of late enrollment, for life. The Part D penalty is a percentage of the national base premium, also for life. Both are avoidable by marking the windows on the family calendar now, the same way the prescription cost guide treats the Part D choices. The free local SHIP counselors (see SHIP counseling) will walk the family through the exact dates for the parent's situation.
The checklist
- Confirm Part A and B enrollment status before the birthday window closes.
- Choose Part D coverage in the first window, even if the parent takes no medicines (the cheapest plan avoids the lifetime penalty).
- Compare Advantage versus Medigap in the first year, when Medigap has no medical underwriting.
- Mark the annual open enrollment window on the calendar every year.
- Update the documents checklist with the Medicare card and the plan documents.
Related guides
Sources & verification
This page is checked against the standards in our editorial policy, preferring government sources for Medicare guidance. Reviewed August 2026:
- Medicare.gov: Medicare Savings Programs (retrieved August 2026)
- Medicare.gov: Medicare Part D drug coverage (retrieved August 2026)
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