Most Medicare penalties and coverage gaps start with one mistake: assuming current insurance automatically allows a delay.
The ordinary age-65 window
The Initial Enrollment Period lasts seven months, beginning three months before your 65th-birthday month and ending three months after it. Signing up before the birthday month generally lets Part B start in the birthday month. Later enrollment usually starts the following month.
Working past 65
You may be able to delay Part B when you or your spouse is still working and you have qualifying group coverage based on that current employment. Ask the employer how the plan coordinates with Medicare. Employer size and coverage type matter.
The COBRA trap
COBRA does not pause the Part B Special Enrollment Period. The eight-month period generally begins when employment or job-based coverage ends, even if COBRA continues. Retiree and Marketplace coverage also should not be assumed to protect against a Part B penalty.
HSA warning
Once enrolled in Medicare, you cannot keep contributing to an HSA. Premium-free Part A can begin retroactively for up to six months when enrollment is delayed, but not before age 65. People working past 65 commonly stop HSA contributions at least six months before applying for Medicare or Social Security and confirm the timing with their tax adviser.
Penalties
The Part B late penalty generally adds 10% for each full 12-month period you could have had Part B but did not, and it usually lasts as long as you have Part B. Part D can add a lasting penalty after 63 or more days without creditable drug coverage.In the RetireNerd Medicare Series
- Medicare Explained: The Complete, Easy-to-Follow Guide
- How Much Does Medicare Cost in 2026? A Realistic Monthly Budget
- Medicare for Married Couples: What Spouses Need to Handle Separately
- Does Medicare Cover Dental, Vision and Hearing?
- What Does Medicare Cover for Free? Preventive Services Explained
- What Medicare Does Not Cover: 10 Gaps to Plan For
- Original Medicare vs. Medicare Advantage: How to Choose
- When to Sign Up for Medicare: Deadlines, Work Coverage and Penalties
- Medicare Part D: How to Compare Drug Plans Every Year
Official resources
- Medicare.gov
- Medicare Plan Compare
- Free, unbiased SHIP counseling
- Sign up for Medicare through Social Security
Educational information only. Medicare rules, costs and plan details can change. Confirm decisions with Medicare, Social Security, your current benefits administrator and a licensed professional when appropriate.