Medicare doesn't have one sign-up season — it has several windows, each with its own job, its own dates, and its own consequences. Here's the whole map.
When: the 7 months around your 65th birthday.
Who it's for: people new to Medicare.
What it does: your first chance to sign up for Part A and Part B.
When: October 15 – December 7, every year.
Who it's for: everyone with Medicare.
What it does: review and change coverage; changes take effect January 1.
When: January 1 – March 31, every year.
Who it's for: people already in a Medicare Advantage plan.
What it does: make one change — switch Advantage plans or return to Original Medicare.
When: January 1 – March 31, every year.
Who it's for: people who missed their IEP.
What it does: sign up for Part A and Part B; coverage starts the month after you enroll — and late penalties may apply.
When: triggered by life events.
Who it's for: people whose circumstances changed.
What it does: opens your own window — losing employer coverage, moving, and similar events.
October 15 through December 7, every year. Anyone with Medicare can use it to join, switch, or drop a Medicare Advantage plan or a Part D drug plan, or to move between Original Medicare and Medicare Advantage. Anything you change takes effect January 1.
Why review at all? Because plans change even when you don't. Each fall, your plan sends an Annual Notice of Change (it should arrive by the end of September) describing what's different next year — costs, covered drugs, networks. Before December 7, three questions are worth five minutes:
If you do nothing, you generally stay in your current plan — even if its costs or coverage changed. "No change" is a decision too; make it on purpose.
January 1 through March 31. If you're enrolled in a Medicare Advantage plan, this window lets you make one change: switch to a different Advantage plan, or leave Advantage and return to Original Medicare (adding a standalone Part D plan if you return). It isn't open to people on Original Medicare, and it can't be used to join Advantage for the first time — that happens during AEP or when you're first eligible.
Windows life opensSome windows aren't on the calendar — they're triggered. Losing job-based coverage, retiring, or moving out of your plan's service area can open a Special Enrollment Period with its own deadline. The most common: when employer coverage ends, you generally get 8 months to sign up for Part B without a penalty. These clocks run whether or not anyone reminds you — if a big change is coming, learn your date before the change, not after.
New to the basics? Start with the ABCD of Medicare →
One page: Parts A through D, the Medigap vs. Medicare Advantage tradeoffs, and the enrollment timeline — in plain English, to keep.
Educational information about how Medicare works — not a plan recommendation or enrollment guidance. Reserve Investment Group, Inc. is a private insurance agency and is not affiliated with the federal government or the federal Medicare program. Medicare plan availability, costs, and coverage vary by state and county and can change over time. For official information, visit Medicare.gov or call 1-800-MEDICARE (1-800-633-4227).
