Moving from an ACA Marketplace Plan to Medicare: The Subsidy Trap to Avoid

If you have been buying your health insurance through the Affordable Care Act marketplace and receiving premium subsidies, turning 65 changes everything, and not everyone gets told how. Once you become eligible for Medicare, you are generally expected to move off your marketplace plan, and the premium subsidies that made it affordable stop applying. People who keep collecting those subsidies after they qualify for Medicare can end up having to repay them at tax time, sometimes thousands of dollars. Getting the timing exactly right protects you from both a coverage gap and a nasty surprise on your tax return.

Bryce's Take

I see this one cause real financial pain. People keep both the marketplace plan and Medicare because nobody told them to cancel, and then the subsidy clawback shows up on their taxes and they owe thousands they never budgeted for. The transition timing has to be exact: end the marketplace plan the day before Medicare starts, no gap and no overlap. If your Part A would not be premium-free, the rules are different and you should not cancel anything until someone has looked at your specific situation.

Why you generally drop the marketplace plan at 65

Most people qualify for premium-free Medicare Part A at 65 because they or their spouse paid Medicare taxes long enough. Once you are eligible for premium-free Part A, you are no longer eligible for the premium tax credits that subsidize a marketplace plan. The marketplace and Medicare are two different systems, and they are not meant to run at the same time for the same person. So at 65 the normal move is to enroll in Medicare and end the marketplace plan rather than keep both.

The subsidy clawback trap

Here is the expensive mistake. The advance premium tax credit that lowers your marketplace premium is reconciled on your tax return. If you continue receiving that subsidy after you became eligible for Medicare, the IRS can require you to pay it back, because you were not eligible for it during those months. People who simply forget to cancel their marketplace plan, or who assume it will end on its own, can find themselves owing back many months of subsidies all at once. The plan does not automatically shut off, and no one from Medicare cancels it for you.

Timing the transition precisely

The goal is a clean handoff with no gap and no overlap. Your Medicare coverage typically begins on the first day of the month you turn 65, or earlier or later depending on your birthday and when you enroll. You want to cancel your marketplace plan so that it ends the day before your Medicare coverage starts. That prevents a gap where you have no coverage and an overlap where you are paying for and receiving subsidies on a plan you should no longer have. Marketplace plans do not cancel automatically when Medicare begins, so you must actively end it through the marketplace.

You cannot use a marketplace plan to supplement Medicare

Some people wonder whether they can keep a marketplace plan alongside Medicare to fill gaps, the way a Medigap plan does. You cannot. It is generally illegal for someone to sell you a marketplace plan knowing you have Medicare, and the marketplace plan is not designed to coordinate with Medicare. If you want to fill Medicare's gaps, the tools are a Medigap plan or a Medicare Advantage plan, not marketplace coverage. Keeping a marketplace plan does not supplement Medicare, it just creates the subsidy problem.

Coordinating the actual enrollment

To make the switch cleanly, enroll in Medicare during your Initial Enrollment Period, the seven-month window around your 65th birthday, so your Medicare start date is set. Then contact the marketplace to end your plan effective the day before Medicare begins. Add a Part D drug plan or a Medicare Advantage plan that includes drug coverage as part of the transition so you do not go without prescription coverage. Missing the coordination on drug coverage is a separate trap that can create a late-enrollment penalty.

If your Part A is not premium-free

There is an exception worth knowing. A small number of people do not qualify for premium-free Part A because they did not accumulate enough work credits. If you would have to pay a premium for Part A, you may not be automatically pushed off marketplace subsidies in the same way, and staying on a marketplace plan can sometimes make sense. This situation is genuinely case-specific, so if you are told you would owe a premium for Part A, get personalized guidance before canceling anything rather than assuming the standard rules apply to you.

Bryce Casson

Licensed Independent Medicare Broker

Bryce Casson is an independent Medicare insurance broker who works with every major carrier. He does not represent any single insurer, which means his recommendations are based on what actually fits each client's situation, not on commissions or quotas.