Every enrollment window that matters in 2026, and the penalties that follow you for life if you miss the wrong one.
There isn't one Medicare enrollment date — there are several, and missing the wrong one can mean a permanent penalty added to your premium for the rest of the time you're on Medicare. Here's every window that matters, in the order most people encounter them.
Your first and most important window. It's a seven-month period centered on the month you turn 65: three months before your birthday month, your birthday month itself, and three months after. For example, someone turning 65 in June 2026 has an IEP running from March 1 through September 30, 2026.
If you miss your IEP entirely and don't qualify for a Special Enrollment Period, the General Enrollment Period runs every year from January 1 through March 31. Coverage now starts the first day of the month after you enroll — a change from the old rule that delayed coverage until July 1. You can only sign up for Part A and/or Part B during the GEP, and a late-enrollment penalty may apply if you didn't have other creditable coverage in the meantime.
If you were covered by an employer group health plan (yours or a working spouse's) past age 65, you generally get an 8-month Special Enrollment Period to sign up for Part B without penalty once that employment or coverage ends — whichever comes first. This is the exception most people rely on to delay Medicare penalty-free while still working.
Running every year from October 15 through December 7, this is the main window for switching Medicare Advantage plans, switching Part D drug plans, or moving between Original Medicare and Medicare Advantage. Changes made during this window take effect January 1 of the following year.
Running January 1 through March 31, this window is only for people already enrolled in a Medicare Advantage plan. It allows one additional plan change per year — switching to a different Medicare Advantage plan or dropping back to Original Medicare (and picking up a stand-alone Part D plan if needed). It is not an opportunity to switch from Original Medicare into Medicare Advantage.
Running December 8 through November 30 each year, this lets you switch into a plan that currently holds a 5-star rating in your area, one time, regardless of what other enrollment window you're in.
Medigap doesn't follow any of the windows above. Your Medigap Open Enrollment Period is a six-month window that starts the day your Part B coverage begins. During that window, insurers must sell you any Medigap policy they offer regardless of health history. Miss it, and in most states insurers can medically underwrite your application going forward — meaning a health condition could raise your premium or get you denied outright. A small but growing number of states offer at least some annual guaranteed-issue access outside this window, so it's worth checking your specific state's rules rather than assuming the six-month window is truly your only shot.
You can typically delay Part B without penalty as long as the employer coverage is considered creditable and comes through active employment (yours or a spouse's) — not retiree coverage, which does not count for this purpose.
Only if you owe a premium for Part A, which most people don't after paying Medicare taxes for at least 10 years. If you do owe a premium, a similar late-enrollment penalty can apply.
Yes — people under 65 who've received Social Security disability benefits for 24 months are generally enrolled automatically, with their own separate 7-month enrollment window built around their 25th month of disability benefits.