If you’re closing in on the window of eligibility for Medicare, which begins at age 65, you may be counting down the days to when you can drop your private or employer-sponsored health insurance and get on this more affordable program.
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However, Medicare coverage has several key deadlines that are essential to qualify in time, not miss out on important coverage and avoid paying penalties. Those penalties can add up to hundreds or even thousands over the reminder of your lifetime.
The Medicare ‘Parts’
Before diving into the enrollment periods and their deadlines, here’s a quick overview of what the different “Parts” of Medicare are for:
- Part A: Hospital insurance (inpatient care, skilled nursing, hospice and some home health)
- Part B: Medical insurance (doctor visits, outpatient care, preventive services and medical equipment)
- Part C: Medicare Advantage (private plans bundling Parts A & B, often Part D plus extras like dental/vision)
- Part D: Prescription drug coverage (helps pay for medications and varies by plan)
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The Initial Enrollment Period (IEP)
The Initial Enrollment Period (IEP) starts three months before your 65th birthday, includes your birthday month and ends three months after. Missing this window can mean waiting until the next enrollment period for coverage to begin. It can also trigger a lifetime penalty: Your Part B premium goes up 10% for every 12-month period you delayed enrollment.
Special Enrollment Period (SEP) for Part B
If you delayed Medicare Part B because you had creditable employer coverage, you’re eligible for a Special Enrollment Period (SEP). This window generally lasts eight months after your employer coverage ends. Miss this and you’ll likely face the same 10% lifetime Part B premium penalty, plus gaps in coverage.
So, here’s what the penalties could look like (using an average 2025 premium of $185):
- 12 months late: 10% x $185 = $18.50 extra per month, every month, for life.
- 24 months late: 20% x $185 = $37 extra per month, for life.
- 36 months late: 30% x $185 = $55.50 extra per month, for life.
The Annual Enrollment Period (AEP) for Part D
Each year from Oct. 15 to Dec. 7, you can join, switch or drop a Medicare Advantage plan or Part D prescription drug plan, with coverage changes taking effect Jan. 1. If you don’t enroll in Part D when first eligible and go more than 63 days without other drug coverage, you’ll face a penalty added to your Part D premium for as long as you have coverage — about 1% of the national base premium for each uncovered month.
Here’s what the penalties for Part D could look like (using the 2025 base premium of $36.78):
- 12 months late: 12% x $36.78 = $4.41 extra per month, every month, as long as you have Part D.
- 24 months late: 24% x $36.78 = $8.83 extra per month (rounded).
The General Enrollment Period (GEP)
For people who missed their Initial Enrollment Period and don’t qualify for a SEP, the General Enrollment Period (GEP) runs from Jan. 1 to March 31 each year. Coverage begins the month after you sign up. But you’ll still pay the lifetime Part B penalty — 10% higher premiums for each 12-month period you delayed enrollment.
Be sure to do whatever you need to do to meet your deadlines, from working with a financial advisor to help you plan all your healthcare needs to setting reminders and having someone hold you accountable to meeting them. The last thing you need at this key stage of life is to pay more money for basic healthcare.
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This article originally appeared on GOBankingRates.com: If You Skip These Medicare Deadlines, It Could Cost You Thousands
