Most Medicare enrollment mistakes share a root cause: not knowing the deadline until it passed. The penalties are permanent, the coverage gaps are expensive, and the rules around exceptions are narrower than people expect.
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Each one triggers a financial penalty, a coverage gap, or both.
Your IEP is 7 months around your 65th birthday. Miss it and you wait for the General Enrollment Period (Jan-Mar), coverage does not start until July, and a 10%-per-year penalty gets added to your Part B premium for life.
COBRA is not "current employer coverage" under Medicare rules. If you turn 65 on COBRA without enrolling in Part B, every month counts toward your late penalty. This catches people who retired early and assumed COBRA had them covered.
The employer-coverage exemption only applies if your employer has 20+ employees. Work for a company with fewer than 20? Medicare becomes primary at 65. Delay Part B and you face penalties plus claims coordination problems.
About 70% of Medicare Advantage enrollees have access to a lower-premium plan but do not switch (KFF, 2024). Formularies, networks, and copays change every year. Auto-renewal keeps you covered but may cost hundreds more than necessary.
Going without Part D drug coverage for 63+ days triggers a permanent penalty when you eventually enroll. The penalty is small per month but adds up over decades. Even if you take no medications today, the insurance cost of skipping is real.
A $0 premium Medicare Advantage plan may have a narrow network, high specialist copays, or prior authorization requirements that cost more than a slightly higher-premium plan. Total cost includes premiums, deductibles, copays, and out-of-pocket maximums.
If you work for an employer with 20 or more employees and have group health coverage through that job, you can delay Part B enrollment without penalty. When you or your spouse stop working (or lose that employer coverage), you get an 8-month Special Enrollment Period to sign up.
The key detail: "current employment" means you or your spouse are still actively working. Retiree health benefits, COBRA, and marketplace plans do not count. If you are unsure whether your situation qualifies, call Social Security at 1-800-772-1213 before your IEP closes. Getting this wrong triggers the penalty; checking costs nothing.
For a full breakdown of every enrollment window and when each applies, see the Medicare enrollment periods guide. For the dollar cost of each missed deadline, see what happens if you miss Medicare enrollment.
Missing the IEP, forgetting to review during Open Enrollment, letting Part D lapse. They all come down to the same thing: the deadline passed before you acted on it. A Medicare enrollment reminder set for the right date turns a "I'll deal with it later" into an email that shows up when it matters.
Missing the Initial Enrollment Period entirely. This triggers a Part B late enrollment penalty of 10% per year added to your premium permanently, plus a potential coverage gap of several months. The second most common mistake is assuming COBRA or retiree coverage exempts you from the enrollment deadline.
It depends on the size of your employer. If your employer has 20 or more employees and you have coverage through them, you can delay Part B without penalty. If your employer has fewer than 20 employees, Medicare becomes your primary insurer at 65 and you should enroll during your IEP to avoid penalties and claims issues.
Part A is free for most people and there is no penalty for late enrollment, so most people sign up at 65. Part B has a premium and a late penalty. If you have qualifying employer coverage, you can delay Part B. Otherwise, enrolling during your IEP at 65 is strongly recommended.
No. COBRA is continuation of former employer coverage, not current employer coverage. If you rely on COBRA past age 65 without enrolling in Part B, you will face a late enrollment penalty when you do sign up. COBRA can supplement Medicare, but it does not replace it or exempt you from enrollment deadlines.
In limited cases. If you were given incorrect information by an employer or Social Security, you may qualify for equitable relief. Contact Social Security at 1-800-772-1213. Otherwise, most enrollment penalties cannot be reversed. The best strategy is preventing the mistake with a timely reminder.
If you chose a Medicare Advantage plan and it does not work for you, the Medicare Advantage Open Enrollment Period (January 1 through March 31) lets you switch plans or return to Original Medicare. During the Annual Open Enrollment (October 15 through December 7) you can make plan changes for the following year.
Free. No account. A reminder before the deadline is the simplest way to avoid a permanent penalty.
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