What to Avoid When Switching to Medicare from the Public Health Exchange

If you’ve been getting health coverage through the Affordable Care Act (ACA) public
Marketplace and you’re about to turn 65, congratulationsyou’ve unlocked a new
level in the health insurance game: Medicare. Unfortunately, the rules are not
printed on the box, and one wrong move can mean permanent penalties, surprise
tax bills, or gaps in coverage just when you really need care.

The good news? With a little planning, you can glide from your Marketplace plan
to Medicare without drama. The bad news? There are some very specific mistakes
you absolutely want to avoid. Think of this guide as your “what not to do”
checklist, built to help you protect your wallet and your health as you make the
switch.

First, Know What’s Actually Changing

The ACA Marketplace (or public health exchange) and Medicare are two completely
different systems:

• Marketplace plans are usually private plans that may be
  subsidized with premium tax credits based on your income.
• Medicare is a federal health insurance program, primarily for
  people 65 and older or those with certain disabilities.

When you become eligible for Medicare, the rules around subsidies, enrollment
deadlines, and what counts as “good enough” coverage all change. That’s why the
transition needs attentionyou can’t just let your Marketplace plan roll and
“add Medicare later” without consequences.

Mistake #1: Waiting Too Long to Enroll in Medicare

The single biggest pitfall is missing your
Initial Enrollment Period (IEP). This is a seven-month window:
the three months before the month you turn 65, your birthday month, and the
three months after.

If you delay signing up for Medicare Part B (medical insurance) and you don’t
have qualifying employer coverage, you can face:

• Lifetime late enrollment penalties on Part B premiums (an
  extra 10% for every full 12-month period you were eligible but not enrolled).
• Waiting for coverage until the next General Enrollment Period,
  which can leave you uninsured for months.

Many people mistakenly think, “I already have a Marketplace plan, so I’m fine.”
Sadly, Medicare doesn’t see it that way. Once you’re eligible for Medicare,
Marketplace coverage is no longer considered a safe fallback for avoiding
Medicare penalties.

Mistake #2: Keeping Your Marketplace Plan and Medicare Without a Plan

Another common misstep is trying to keep your ACA plan after you enroll in
Medicare “just in case” or because you like the network better. In reality, this
can backfire:

• Marketplace coverage doesn’t coordinate with Medicare the way
  an employer plan might.
• You may end up paying two full premiums but only using one
  plan.
• In many cases, the Marketplace plan will not pay for services
  that Medicare should cover first.

In short: once you’re on Medicare, the Marketplace plan usually becomes
expensive “extra noise,” not useful secondary coverage. If you want additional
protection beyond Original Medicare, you’re generally looking at
Medicare Advantage or a Medigap (supplement)
plan, not a Marketplace plan.

Mistake #3: Forgetting to End Your Marketplace Coverage (and Subsidies)

Here’s a sneaky one: Marketplace coverage
does not end automatically when Medicare starts. You have to
log into your Marketplace account or call and actively terminate coverage for
the person(s) moving to Medicare.

If you’ve been getting premium tax credits (the subsidies that
lower your monthly Marketplace premium), things get more serious:

• Once you’re eligible for premium-free Medicare Part A, you’re generally
  no longer eligible for those subsidies.
• If you keep taking them anyway, you may have to
  pay them back at tax time.

So, one of your first “to-dos” is to report your Medicare start date to the
Marketplace and end coverage for yourself as of the day before Medicare kicks
in. If your spouse or dependents need to stay on the Marketplace plan, make sure
you only end coverage for you, not the whole household.

Mistake #4: Not Getting Drug Coverage (or Assuming Your ACA Plan Counts)

Original Medicare doesn’t cover most outpatient prescriptions. That’s where
Part D prescription drug plans or Medicare Advantage plans with
drug coverage come in.

If you delay enrolling in Part D and you don’t have other
creditable coverage (drug coverage that’s at least as good as
standard Medicare Part D), you can face a permanent late penalty
added to your Part D premium for as long as you have Medicare prescription
coverage.

Key point: your ACA Marketplace plan is not considered “creditable coverage”
once you’re eligible for Medicare. It may have been great drug coverage before,
but Medicare uses its own rules. If you’re switching, make sure you:

• Enroll in a Part D plan or a
  Medicare Advantage plan with built-in drug coverage, and
• Time the start so you don’t have a gap between your Marketplace plan ending
  and your Medicare drug coverage beginning.

Mistake #5: Assuming Marketplace Cost-Sharing Help Carries Over

If your income was low on the Marketplace, you might have enjoyed
cost-sharing reductionslower deductibles, copays, and
out-of-pocket maximums. Unfortunately, those savings don’t move with
you to Medicare.

Medicare has its own cost-sharing structure: deductibles, 20% coinsurance for
many Part B services, and separate rules for hospital stays and skilled nursing.
To help with those costs, you might:

• Choose a Medicare Advantage plan with a predictable out-of-
  pocket limit, or
• Buy a Medigap plan that helps pay Medicare’s deductibles and
  coinsurance.
• See if you qualify for Extra Help with drug costs or a
  Medicare Savings Program to help with premiums and
  cost-sharing.

The big “don’t” here is assuming Medicare will be free or almost free just
because your Marketplace plan was heavily subsidized. Plan ahead for your new
cost structure.

Mistake #6: Ignoring Special Enrollment Period Rules

The Marketplace and Medicare both use
Special Enrollment Periods (SEPs), but they work differently.

On the Marketplace side, losing qualifying coveragelike your Marketplace plan
ending when Medicare startscan trigger a SEP to pick a new Marketplace plan
for other family members. On the Medicare side, SEPs let you:

• Change Medicare Advantage or Part D plans when you move or lose other
  coverage.
• Avoid penalties if you delayed Medicare because you had qualifying large
  employer coverage.

Where people get in trouble is assuming that losing Marketplace coverage
automatically creates some magical, penalty-free window to enroll in Medicare
late. That’s not how it works. If you miss your Initial Enrollment Period and
you don’t meet very specific criteria, you may still face penalties and wait
months for coverage to start.

Mistake #7: Failing to Think About Taxes and Income

The Marketplace is built around your projected income. Your
premium tax credits are based on what you expect to earn for the year, and the
final numbers are reconciled on your tax return.

Once Medicare enters the picture:

• If you keep a Marketplace plan and subsidies past the point you’re eligible
  for Medicare, you may have to repay those credits.
• If your income rises in retirement (from Social Security, pensions,
  withdrawals), you might also run into IRMAAan income-related
  surcharge that raises your Part B and Part D premiums if your income is above
  certain thresholds.

The takeaway: when you’re planning the switch from the public exchange to
Medicare, it’s smart to look at the tax side too. Adjust your
Marketplace coverage end date, your income estimates, and your withdrawal
strategy so there are no nasty surprises in April.

Mistake #8: Not Comparing Medicare Advantage, Medigap, and Original Medicare

On the Marketplace, you probably compared bronze, silver, gold, and platinum
plans. With Medicare, your big menu looks like this:

• Original Medicare (Part A & Part B) + Part D + optional Medigap
• Medicare Advantage (Part C)bundled plans that usually include
  drug coverage and often extras like dental, vision, and hearing.

A major “don’t” is assuming that the first Medicare Advantage plan you see on a
postcard is automatically your best option. Instead:

• Check that your doctors and hospitals are in-network.
• Confirm that your prescriptions are on the formulary and what
  they’ll cost.
• Compare annual out-of-pocket limits, not just premiums.
• Consider whether you value network flexibility (often better
  with Original Medicare + Medigap) or lower premiums and extra
  benefits (often better with Medicare Advantage).

Since you’re already used to shopping carefully on the Marketplace, bring that
same comparison mindset to Medicarejust don’t assume the rules are the same.

Mistake #9: Going It Alone When Free Help Exists

Both the Marketplace and Medicare are complicated, but Medicare rules can feel
especially maze-like. The last thing you want is to DIY your way into penalties
that last as long as you’re alive.

Instead of guessing:

• Reach out to your state’s SHIP (State Health Insurance Assistance
  Program) for free, unbiased counseling.
• Talk to a licensed Medicare agent, such as professionals at a
  firm like Select and Insure, who specialize in transitions from the public
  exchange to Medicare and can walk you through plan options step by step.
• Use the official Medicare Plan Finder tool to compare drug and
  Advantage plans based on your medications and preferred pharmacies.

The mistake isn’t asking for help. The mistake is not asking
and hoping it will all make sense eventually.

How to Time the Switch: A Simple Checklist

To avoid the biggest traps, use this basic roadmap:

1. About 6–9 months before turning 65: Learn the basics of
   Medicare Parts A, B, C, and D. Start a list of your doctors, medications, and
   must-have benefits.
2. 3–4 months before turning 65: Compare estimated Medicare costs
   with your current Marketplace plan. Decide whether you’ll lean toward Original
   Medicare + Medigap or Medicare Advantage.
3. During your Initial Enrollment Period: Enroll in Part A and
   Part B (unless you have a very specific reason not to). Add Part D or pick a
   Medicare Advantage plan with drug coverage.
4. As soon as your Medicare start date is confirmed: Contact the
   Marketplace and schedule your Marketplace coverage to end the day before
   Medicare goes livefor you only, if others in your household are staying
   on-exchange.
5. After the switch: Confirm your new ID cards, pharmacy, and
   provider networks. Keep an eye on bills in the first few months to make sure
   claims are being processed correctly.

Real-World Experiences: What People Wish They’d Done Differently

The rules are one thing. Real life is another. To bring this all down to earth,
here are some composite examples based on the kinds of situations people run
into when switching from the Marketplace to Medicare.

“I Thought My Marketplace Plan Would Protect Me from Penalties”

Imagine Susan, who turned 65 last year. She loved her silver-tier Marketplace
planher doctors were in-network, she had a low deductible, and thanks to
subsidies, the premium was manageable. When she started getting Medicare
mailings, she thought, “I’ll just stick with my current plan a little longer and
sign up for Medicare when I retire for real.”

The problem? Medicare didn’t care that she still had a great Marketplace plan.
By the time she finally enrolled in Part B, she was outside her Initial
Enrollment Period and didn’t qualify for any special exceptions. Her monthly
Part B premium is now permanently higher because of the late enrollment penalty,
and she had a several-month gap in comprehensive coverage during the transition.
Her comment after learning all this: “I wish someone had told me that my
Marketplace plan didn’t ‘count’ anymore once Medicare was on the table.”

“I Forgot to Turn Off the Subsidies”

Then there’s Mark. He did enroll in Medicare on timegreat! But he never went
back to the Marketplace website to end his plan. The premiums continued to be
paid, still showing a big discount from the advanced premium tax credits he had
qualified for earlier in the year.

At tax time, his accountant had bad news: once he became eligible for
Medicare, those subsidies shouldn’t have been applied. He had to repay several
months’ worth of premium tax credits on his return. Medicare enrollment wasn’t
the issue; forgetting to officially shut down the Marketplace coverage and
subsidies was.

Mark’s takeaway: “Canceling my old plan felt like a tiny admin step, so I put it
off. That little bit of procrastination cost me hundreds of dollars later.”

“I Didn’t Realize My Drug Coverage Would Change So Much”

Consider Angela, who takes three brand-name medications. Her Marketplace plan
had a pretty generous drug formulary, and she rarely thought about the details
because her copays were predictable.

When she moved to Medicare, she picked a low-premium Part D plan without
carefully checking the formulary and pharmacy pricing. Within a couple of
months, she realized:

• One of her medications was in a higher tier, with much larger copays than she
  expected.
• Another required prior authorization, creating delays in refills.
• Her preferred local pharmacy wasn’t considered “preferred,” so her costs were
  higher than they needed to be.

Could she change plans? Eventually, yesbut she had to wait for the appropriate
enrollment period. Her reflection: “I assumed my new coverage would act like my
old ACA plan. If I had used the Medicare Plan Finder and matched my drugs more
carefully, I could’ve saved a lot of frustration.”

“Talking to an Advisor Made Everything Easier”

Finally, meet a happier story: Robert and Linda, a married couple where Robert
was on a Marketplace plan and Linda was already on Medicare. As Robert
approached 65, they decided they didn’t want to guess. They spoke with a
licensed Medicare specialist at a local agency similar to Select and Insure.

During that conversation, they:

• Confirmed the exact date Robert’s Medicare would start and how to enroll in
  Parts A and B.
• Compared several Medicare Advantage and Medigap options, based on Robert’s
  doctors and medications.
• Set a precise end date for his Marketplace coverageone day before Medicare
  startedwhile keeping Linda’s coverage unchanged.
• Reviewed how the transition would affect their taxes and future healthcare
  costs.

The result? No penalties, no gaps in coverage, and no surprise tax repayments.
Robert’s summary: “The rules are complicated, but once someone walked us through
the timeline, it felt manageable. The biggest relief was knowing we weren’t
accidentally leaving money on the table or breaking any rules.”

Bottom Line: Plan the TransitionDon’t Wing It

Moving from the public health exchange to Medicare isn’t just another plan
changeit’s a full change in systems. The biggest dangers are invisible:
penalties you don’t feel until later, subsidies you don’t realize you’re not
supposed to be getting, or coverage gaps that only matter when you get sick or
injured.

If you remember nothing else, remember this: don’t wait, don’t
assume, and don’t go it alone. Start planning months before your 65th
birthday, double-check how and when to end your Marketplace plan, make sure you
have Medicare drug coverage lined up, and get help from trusted experts when
you need it.

With a clear plan and the right guidance, your transition from the public health
exchange to Medicare can be smooth, predictable, and penalty-freefreeing you up
to focus on enjoying the next chapter of life, not decoding health insurance
fine print.