The Part B Late Enrollment Penalty
If you don't sign up for Medicare Part B when you're first eligible — and don't have qualifying employer-sponsored coverage to justify the delay — you'll pay a permanent late enrollment penalty. The penalty adds 10% to your Part B premium for each 12-month period you were eligible but didn't enroll.
This penalty never goes away. It stays with you for as long as you have Part B.
Example: You delay Part B enrollment for 3 full years (36 months = three 12-month periods). Your penalty is 30% added to the standard premium permanently. In 2025, the standard premium is $185/month. With a 30% penalty, you'd pay $240.50/month — every month — for the rest of your Medicare life. Over a 20-year retirement, that's an extra $13,320.
The Part D Late Enrollment Penalty
The Part D prescription drug penalty works differently but accumulates just as painfully. For each month you were eligible for Part D but didn't have creditable drug coverage, you'll pay 1% of the national base beneficiary premium for that year, multiplied by the number of months without coverage.
In 2025, the national base beneficiary premium is $36.78/month. If you went 18 months without creditable Part D coverage, your penalty is 1% × 18 = 18%, or about $6.62/month added to your Part D premium. Like Part B, this penalty is permanent — and it recalculates each year as the national base premium changes.
The simplest way to avoid this penalty: enroll in a basic Part D plan when you first become Medicare-eligible, even if your current drug costs are low. A basic plan can cost as little as $10–$20/month — far cheaper than the penalty you'd accumulate by waiting.
The Medigap Enrollment Window (This One's Different)
There's no direct government fine for missing your Medigap Open Enrollment Period, but the consequences can be far more costly than any premium penalty. During your OEP — the 6-month window that starts when you turn 65 and have Part B — insurance companies must sell you any Medigap plan at standard rates, regardless of your health history.
Once your OEP closes, in most states (including Wyoming and Utah), insurers can use medical underwriting. They can deny your application, charge significantly higher premiums, or exclude pre-existing conditions from coverage — based on your health status.
If you develop a serious condition after your OEP ends — diabetes, heart disease, cancer, COPD — you may be permanently uninsurable for Medigap, or only able to buy it at prohibitive premiums. This is the most underappreciated risk in Medicare planning.
When Penalties Don't Apply
The most important exception: if you have creditable health coverage through an active employer (your own or your spouse's), you can delay Medicare enrollment without penalty. When that coverage ends, you have a Special Enrollment Period — 8 months for Part B and 63 days for Part D — to enroll without incurring penalties.
Key clarification: COBRA continuation coverage does NOT count as creditable coverage for this purpose. If you lose employer insurance and choose COBRA, your Special Enrollment Period clock has already started. Don't assume COBRA buys you more time to enroll in Medicare — it doesn't.
Get written confirmation from your employer's HR department stating that your coverage is creditable. Keep that letter. If Social Security or Medicare ever questions your enrollment timing, that documentation is your protection.
What to Do If You've Already Been Penalized
If you believe you were penalized incorrectly — or if you had qualifying coverage that wasn't properly documented — contact Social Security to request a review. If your penalty was assessed based on inaccurate information, you can appeal with supporting documentation.
If the penalty stands, a good Medicare advisor can help you evaluate your overall plan structure to minimize costs going forward. Sometimes switching to a Medicare Advantage plan (which bundles Part B, Part D, and often extra benefits) can offset penalty costs through lower overall out-of-pocket spending.
The best move, of course, is to get the enrollment timeline right from the beginning — which is exactly what we help our clients do.
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