When to Enroll in Medicare (Without Getting Hit by a Late Penalty)
By Logan Steele · June 22, 2026 · 6 min read
Medicare has a generous welcome window. It also has a long memory for the people who miss it. The late-enrollment penalty for Part B is permanent — it follows you for the rest of your life — so this is one of those rare situations where timing genuinely matters more than plan choice.
Here's the calendar in plain English.
Your Initial Enrollment Period (IEP)
Seven months long, centered on the month you turn 65. Three months before your birthday month, your birthday month, and three months after. If you sign up in the three months before, your coverage starts the month you turn 65. Sign up later in the window and coverage starts the month after you enroll.
If you're already drawing Social Security, you get auto-enrolled in Parts A and B. If you're not (and many people aren't anymore), nobody calls. You have to enroll yourself at ssa.gov/medicare.
Still working at 65?
If you have creditable employer coverage through a company with 20+ employees, you can delay Part B without penalty. When you eventually leave that coverage, you get an 8-month Special Enrollment Period (SEP) to sign up — no penalty, no waiting.
Two important traps:
- COBRA does not count as creditable coverage for Part B. Losing employer coverage starts the 8-month clock — using COBRA doesn't pause it.
- HSA contributions stop the moment you enroll in any part of Medicare, including Part A. If you're still working and contributing to an HSA, delay all parts.
The General Enrollment Period (GEP)
Missed your IEP without creditable coverage? You can enroll Jan 1 – Mar 31, with coverage starting the month after enrollment. The catch: this is where the penalties live.
The penalties (and they're permanent)
| Part | Penalty | How long |
|---|---|---|
| Part B | +10% per full 12-month delay | For life |
| Part D | +1% of the national base premium per month without coverage | For life |
| Part A (rare) | +10% if you owe a premium and were late | Twice the number of years you delayed |
Example: skip Part B for 3 years without creditable coverage and your premium is 30% higher — every month, forever.
The Annual Enrollment Period (AEP)
October 15 – December 7 each year. This is when anyone already on Medicare can switch Advantage plans, switch Part D plans, or move between Original Medicare and Advantage. Changes take effect January 1. If your meds, doctors, or plan costs changed this year, this is your annual checkup window.
The Medicare Advantage Open Enrollment Period
January 1 – March 31. If you're already in a Medicare Advantage plan, you get one chance to switch to a different Advantage plan or drop back to Original Medicare. Original-to-Advantage doesn't happen here — that's AEP.
When you first enroll in Part B at 65 or later, you get a one-time 6-month Medigap Open Enrollment window with guaranteed issue — no medical questions. After that window closes, Medigap insurers in most states can ask health questions and decline you. This is the single most overlooked deadline in Medicare.
The takeaway
Mark three things on the calendar: the 7-month window around your 65th birthday, your 6-month Medigap guarantee window starting the day Part B kicks in, and AEP every fall once you're enrolled. Get those three right and the rest is mostly plan shopping.
Not sure where you fall on the calendar? That's a 10-minute call.
Educational only — not legal or tax advice. Enrollment rules and windows can change; confirm with Social Security or a licensed agent before acting.