Medicare Enrollment in 2026: When to Sign Up, What to Avoid, and the Decisions That Matter

Martin turned 65 in June. He was still working at a company with 12 employees. His employer offered health insurance, and he figured he was covered — no need to worry about Medicare yet.

He was wrong. His employer had fewer than 20 employees, which meant his private plan became secondary to Medicare at 65. Medicare was primary — whether he enrolled or not.

He didn't enroll. He ran up $40,000 in medical bills that his private insurer refused to pay as primary. And when he finally enrolled in Medicare a year later, he faced a permanent 10% Part B premium penalty.

Medicare enrollment is surprisingly unforgiving. The rules have exceptions, but the exceptions have exceptions. Here is the map.

Medicare: The Four Parts

Parts A and B together are "Original Medicare." You then choose either a Medigap supplement (to fill in the gaps in Original Medicare) or Medicare Advantage (Parts A+B bundled with extras).

The Initial Enrollment Period

Your Initial Enrollment Period (IEP) is a 7-month window:

• 3 months before the month you turn 65
• The month you turn 65
• 3 months after the month you turn 65

Enrollment timing and your start date:

To start coverage on your 65th birthday, enroll in the 3 months before your birthday month.

When You Can Delay Medicare (Without Penalty)

You may delay without penalty if you have qualifying employer coverage:

Qualifying (can delay):

• Active employment coverage from your own employer with 20+ employees
• Active employment coverage from a spouse's employer with 20+ employees

Not qualifying (must enroll at 65):

• Retiree coverage (former employer)
• COBRA coverage
• Marketplace/ACA coverage
• Coverage from employer with fewer than 20 employees
• VA health coverage

When qualifying employer coverage ends, you get a Special Enrollment Period — 8 months to enroll in Part B without penalty.

The Permanent Late Enrollment Penalties

Missing enrollment windows without qualifying employer coverage triggers penalties that last for life:

Part B penalty: 10% added to your standard premium for each full 12-month period you were eligible but didn't enroll.

• If you waited 2 years to enroll: 20% permanent premium surcharge
• In 2026: $185.00 × 120% = $222.00/month, every month, for life

Part D penalty: 1% of the national base beneficiary premium per month without creditable drug coverage.

• 2026 base premium: approximately $35.00/month
• 24 months without coverage: 24% penalty = $8.40/month, permanently

These penalties are not one-time. They're added to your premium every month for as long as you have Medicare. A 2-year delay in Part B costs roughly $37/month in permanent additional premium — $444/year for the rest of your life.

The Medigap vs. Medicare Advantage Decision

Once enrolled in Original Medicare (Parts A + B), you face a second major decision: how to cover the gaps.

Original Medicare + Medigap (supplement) + Part D:

• Freedom to use any Medicare-accepting provider in the U.S. (no networks)
• More predictable out-of-pocket costs (Medigap covers most of what Medicare doesn't)
• Higher premiums (Medigap + Part D is typically $250–$500+/month for the supplement)
• Medical underwriting applies if you switch later (except during Medigap Open Enrollment Period at 65)

Medicare Advantage (Part C + D bundled):

• Lower monthly premiums (often $0 above Part B)
• Network restrictions (HMO/PPO) — must use in-network providers or pay more
• Often includes extras (dental, vision, fitness)
• Prior authorizations required for some services
• Out-of-pocket costs can be higher for complex care

The critical timing issue: Medigap Open Enrollment — the 6-month period after Part B starts — is your only chance to buy a Medigap plan with no medical underwriting. Outside that window, insurers can reject you or charge more based on health.

If you choose Medicare Advantage at 65 and want to switch to Medigap at 70, you may not be able to due to health conditions that developed in the intervening years.

Many advisors recommend considering a Medigap plan at 65 if you can afford the premiums and value the flexibility. It's easier to switch from Medigap to Medicare Advantage later than the reverse.

Annual Enrollment Period

Every year from October 15 to December 7, you can:

• Switch Medicare Advantage plans
• Add, drop, or switch Part D plans
• Switch from Medicare Advantage back to Original Medicare (though Medigap may be harder to get)

Changes take effect January 1 of the following year.

The 2026 Medicare Cost Overview

Medicare enrollment is a once-in-a-lifetime decision with penalties for mistakes and narrow windows for correction. Make it carefully, and ideally with guidance from someone who understands both the insurance and the tax implications.

Connect with a retirement advisor who can walk through your Medicare options alongside your overall retirement income plan.