Do you need to sign up for Medicare at 65 if you have other coverage?

If you turn 65 and already have comprehensive health insurance, you don’t necessarily have to enroll in Medicare. In some situations, though, enrolling at 65 is essential to avoid coverage gaps and penalties.

When enrolling at 65 makes sense

  • Potentially lower costs. Medicare may have lower premiums, deductibles, or out-of-pocket costs than your current plan.
  • Broader access to providers. Original Medicare lets you see any doctor or hospital nationwide that accepts Medicare. If you’re considering Medicare Advantage, compare its network to your existing plan’s network.
  • Penalty avoidance. If you delay and don’t qualify for a Special Enrollment Period (SEP), you could owe lifetime premium penalties.

When delaying Medicare may be you best option (with employer coverage)

If you’re satisfied with your employer-sponsored insurance, delaying Part B can save you the monthly premium while you remain covered as an active employee—or as a spouse on an active employee’s plan.

Important note regarding Health Saving Account (HSA) users

Enrolling in any part of Medicare makes you ineligible to contribute to a Health Savings Account (HSA), even if you keep your HSA-qualified plan alongside Medicare. Because Part A can be retroactive for up to six months when you later enroll, plan to stop HSA contributions six months before your Medicare start date to avoid tax issues.

How employer size affects what you should do

You can have group coverage and Medicare at the same time. Which payer is primary depends on employer size:

  • Fewer than 20 employees: Medicare is generally primary and the group plan is secondary. Some small-group plans may refuse to pay for services Medicare would have covered if you don’t enroll in Medicare—leaving you under-insured. Confirm the rules with your employer before you become Medicare-eligible.
  • 20 or more employees: The group plan is primary and Medicare is secondary. Many people delay Part B in this situation to avoid the premium and then enroll during an SEP—any time while covered as an active employee or within eight months after that active coverage ends.

Examples of Delaying Medicare Part B Enrollment

Example 1: Actively employed individual

Situation: Mark, 66, works full time for a company with more than 20 employees. He and his wife are covered by his employer’s plan with comprehensive benefits and creditable prescription coverage.
Why they delay: Because the employer has 20+ employees, the group plan pays first. Mark delays Part B to avoid the premium while he’s still working.
What they do: Mark takes premium-free Part A but defers Part B. They will enroll during an SEP after he retires, so they won’t face late-enrollment penalties.

Example 2: Spouse covered by an active worker’s plan

Situation: Diane, 67, is retired; her husband, Paul, works for a large employer. She’s covered under Paul’s plan.
Why they delay: Because Paul is actively employed at a 20+ employee company, Diane’s coverage is considered creditable, so she can delay Medicare without penalties.
What they do: Diane stays on Paul’s plan and doesn’t enroll in Parts B or D. When Paul retires, she’ll use her SEP to enroll in Medicare.

Example 3: Individual contributing to an HSA

Situation: Susan, 65, has a high-deductible plan and wants to keep contributing to her HSA.
Why they delay: Enrolling in any part of Medicare would end her ability to contribute to an HSA.
What they do: Susan delays all parts of Medicare (including Part A) so she can continue HSA contributions. She plans to stop contributing six months before she enrolls and then use her SEP when she retires.