Who Must Enroll in Medicare at 65? The Five Groups That Can’t Wait

For many Americans, turning 65 is a milestone not just in life but in healthcare. While some people can delay Medicare without penalty, others are required to enroll immediately to avoid costly mistakes. Knowing which group you fall into can mean the difference between smooth coverage and a lifetime of penalties.

The Five Groups Required to Enroll at 65

1. No Employer or Group Coverage
   If you’re not working and don’t have insurance through your own job or your spouse’s employer plan, Medicare enrollment at 65 is mandatory. Failing to sign up leaves you uninsured and subject to penalties.
2. Employees of Small Companies (19 or Fewer Employees)
   For workers at small businesses, Medicare becomes the primary payer at age 65, and the employer’s plan shifts to secondary coverage. If you don’t enroll in Medicare, you could be responsible for most of your medical bills.
3. ACA, Marketplace, or Obamacare Plans
   Affordable Care Act (ACA) plans stop making financial sense once you turn 65. Premium credits and tax subsidies vanish, and you’re required to transition to Medicare. Staying on ACA could cost you far more than switching.
4. Retired Military with Tricare or Tricare for Life
   Tricare requires enrollment in Medicare Part B at age 65. Without it, you risk losing Tricare coverage and may face permanent late enrollment penalties. Active-duty military are the only exception until their service ends.
5. COBRA Participants
   If you’re on COBRA when you turn 65, you still need to enroll in Medicare. COBRA drops to secondary coverage, paying only 20% of claims—leaving you responsible for the other 80% if you don’t sign up for Medicare.

Enrollment Timeline and Process

Your Initial Enrollment Period (IEP) begins three months before your 65th birthday, includes your birth month, and extends three months after. Enrolling early ensures coverage starts the first day of your birth month. Waiting until or after your birthday can delay coverage by up to three months.

• Already on Social Security? You’ll be enrolled automatically, with your Medicare card arriving about 100 days before your birthday.
• Not on Social Security? You must enroll yourself either at ssa.gov, by submitting paper forms, or with help from a Medicare educator.

Penalties for Missing the Deadline

The stakes are high if you miss your Medicare Part B enrollment:

• 10% penalty added to your premium for every 12 months of delay.
• Penalties last for life.
• For Tricare members, skipping enrollment risks losing Tricare altogether.
• COBRA participants without Medicare at 65 could face massive out-of-pocket costs, as COBRA won’t cover what Medicare should.

How Medicare Coordinates with Other Coverage

When you turn 65:

• Small employer plans, Tricare, and COBRA all move to secondary status, meaning Medicare pays first.
• Tricare + Medicare together provide excellent, comprehensive coverage, including drug benefits.
• COBRA can still cover younger spouses or dependents, but the primary enrollee must transition to Medicare.

Getting Help with Enrollment

Navigating Medicare’s rules can feel overwhelming, but you don’t have to do it alone. Experts like Erica Smiley at MedicareSchool.com help seniors:

• Understand whether they need to enroll at 65
• Compare plan options (Medigap, Advantage, Part D)
• Avoid penalties and gaps in coverage

If you’re approaching 65, review your coverage early, check your Initial Enrollment Period dates, and get help if you’re unsure. A misstep could cost you for life.