Medicare Enrollment Checklist

Why does a benefit you earned come with penalties that never go away? Because Medicare runs on deadlines, and miss the wrong one and you pay a surcharge for the rest of your life. This checklist puts every window on a timeline so you enroll on schedule, not late and not by accident.

The cruel part is the lifetime nature of the mistakes. A late Part B penalty isn’t a one-time fee. It’s added to your premium permanently, climbing 10% for each year you should have been enrolled and weren’t. Missing the window is the expensive error this checklist exists to prevent.

The windows it tracks

• Three months before 65. Your Initial Enrollment Period opens. It runs the three months before your birthday month, the month itself, and three months after. Act in the first half so coverage starts on time.
• If you’re still working at 65. With true employer coverage you may be able to delay Part B without penalty, but the rules are narrow and COBRA and retiree plans usually don’t count. The checklist makes you confirm before you delay, not assume. Walk through Medicare at 65 while still working first.
• The 8 months after employer coverage ends. That’s your Special Enrollment Period for Part B. Miss it and you wait, and you pay.
• Annual open enrollment, October 15 to December 7. Every year, you re-shop your Part D drug plan and your Advantage plan. Plans change their formularies, and last year’s best plan can quietly become this year’s worst.

Decisions to make before you enroll

The checklist doesn’t just track dates. It forces the choices that come with them.

• Original Medicare with a Medigap supplement, or Medicare Advantage. This fork is hard to reverse later, so decide it deliberately.
• A Part D drug plan that actually covers your prescriptions.
• Whether your income triggers a surcharge.

The surcharge nobody warns you about

Here’s the second-order cost. On top of the standard 2026 Part B premium of $202.90 a month, higher earners pay IRMAA, an income-based surcharge that starts above $109,000 of income for a single filer and $218,000 for a couple. It runs on a two-year lookback, so your 2026 premium reflects your 2024 income. The Roth conversion or asset sale you do today can raise your Medicare premium two years from now, which is why enrollment and tax planning belong on the same page.

Mark the dates the day you turn 64 and a half. Medicare rewards the early and punishes the late, and the punishment is for keeps. Get the windows right and the rest is just paperwork.