Most Medicare questions have a range of reasonable answers. This one does not. There is a rule about health savings accounts and Medicare that catches people every year, it is easy to trip over without knowing, and it can result in a tax bill for something you did in good faith.
The short version: once you enroll in any part of Medicare, you can no longer contribute to a health savings account. And because Part A can be backdated up to six months, you may find that contributions you made months before you signed up were not allowed either.
That six-month lookback is the part almost nobody is told about.
What actually changes when I go on Medicare?
Two things change, and they are often confused with each other.
You can no longer contribute to an HSA. That applies from the month your Medicare coverage begins, and it applies to any part of Medicare, including Part A on its own.
But the account does not go away. The money that is already in there stays yours. It keeps its tax advantages, it can keep growing, and you can keep spending it on qualified expenses for as long as it lasts. Nothing is forfeited and there is no deadline to empty it.
So the change is one-directional. Money can come out. It can no longer go in.
What is the six-month lookback, and why does it catch people?
Here is where it gets specific.
When you enroll in Medicare Part A after your 65th birthday, coverage can be made retroactive for up to six months, though not earlier than the first month you were eligible. That retroactive start is not optional and you generally cannot decline it.
Which means the date you signed up is not necessarily the date your Medicare coverage began for HSA purposes.
Take a common example. Someone works past 65 and keeps contributing to an HSA through their employer. At 66 and a half they retire and enroll in Medicare in July. Part A is backdated to January. Every HSA contribution they made from January onward was made while they were technically enrolled in Medicare, and those contributions were not permitted.
They did nothing careless. They simply were not told that signing up in July could reach backward into January.
What happens if I contributed when I should not have?
Excess contributions are not ignored, but they are usually fixable.
Contributions made while you are enrolled in Medicare are treated as excess contributions. Left in place they can be subject to tax and an additional penalty. The way to resolve it is generally to withdraw the excess amount, along with any earnings attributable to it, before the deadline for filing your return.
This is one of the few Medicare-adjacent problems where the right person to call is a tax professional rather than an insurance agent. The correction has to be handled properly with your HSA custodian and reported correctly, and I would rather tell you that than guess at it.
What I can tell you is that the sooner you catch it, the simpler it is.
Can I delay Medicare to keep contributing?
Sometimes, and this is a genuine strategy rather than a loophole. But it depends on your employer and it interacts with Social Security in a way that surprises people.
If you are still working, have coverage through an employer with 20 or more employees, and that coverage qualifies as creditable, you may be able to delay Part B without a late enrollment penalty. Some people in that situation also delay Part A specifically so they can keep contributing to an HSA.
Two things make this fail.
If your employer has fewer than 20 employees, Medicare generally pays first, which changes the calculation entirely and usually means delaying is a bad idea. I have written more about working past 65 and employer coverage.
And if you are drawing Social Security, you cannot decline Part A. Enrollment in Part A is automatic for people receiving Social Security benefits, and to refuse it you would generally have to withdraw from Social Security and repay what you have received. For most people that is not a realistic trade.
So the strategy is available to a narrower group than people assume: still working, larger employer, creditable coverage, and not yet drawing Social Security.
What can I spend HSA money on once I am on Medicare?
More than most people realize, and this is where the account earns its keep in retirement.
You can generally use HSA funds tax-free for qualified medical expenses, which continues after you enroll in Medicare. That includes many out-of-pocket costs you will actually have: deductibles, copays, coinsurance, dental, vision and hearing expenses that Medicare does not cover, and certain long-term care services.
You can also generally use HSA funds to pay Medicare Part B, Part D and Medicare Advantage premiums. That is a meaningful use for a lot of people, because those premiums are a recurring cost for the rest of your life.
The significant exception is Medicare Supplement premiums. Medigap premiums are generally not a qualified expense for HSA purposes, and that catches people who assumed all Medicare-related premiums were treated the same way.
So the account can absorb a real share of your ongoing costs. It just cannot absorb the Medigap premium.
Should I spend it down or leave it alone?
There is no single answer, but there is a useful way to think about it.
The account keeps its tax advantages while it is invested, so there is no forced spend-down and no deadline. Some people leave it untouched and let it grow as a reserve against the costs that come later, which is exactly the period when medical spending tends to rise.
What is worth knowing is what happens to the account when you die, because the treatment differs depending on who inherits it, and a spouse is treated differently from a non-spouse beneficiary. That is a conversation to have with whoever handles your taxes, and it is worth having before it matters rather than after.
If you have a meaningful balance and no plan for it, that is the gap worth closing.
What should I check before I enroll?
Four things, and the first one is the whole article.
Work out your actual Medicare start date, including any retroactive Part A. Not the date you plan to sign up. The date coverage will be treated as beginning.
Stop HSA contributions in time, counting back from that date rather than from your signup date.
Ask your employer or plan administrator, in writing, whether your coverage is creditable, because that word decides whether delaying is safe.
Talk to whoever prepares your taxes before you enroll, not after, particularly if you have been contributing this year.
If you want to talk through the Medicare side of it, call me at 512-844-3983. I am an independent agent licensed in multiple states. I will tell you plainly when a question belongs with your tax professional rather than with me, and this is an area where part of it does.
Frequently asked questions
Can I contribute to an HSA once I am on Medicare?
No. Once you are enrolled in any part of Medicare, including Part A alone, you can no longer make HSA contributions. The month your coverage begins is the cutoff.
What is the six-month lookback?
When you enroll in Part A after 65, coverage can be backdated up to six months, but not before the first month you were eligible. Contributions made during that retroactive period were not permitted, even though you had not signed up yet.
Do I lose the money in my HSA when I go on Medicare?
No. The balance stays yours, keeps its tax advantages, and can be spent on qualified expenses indefinitely. Only new contributions stop.
Can I use HSA funds to pay Medicare premiums?
Generally yes for Part B, Part D and Medicare Advantage premiums. Medicare Supplement premiums are generally not a qualified expense, which is the exception people miss.
Can I refuse Part A so I can keep contributing?
Only in limited circumstances, and not if you are drawing Social Security, since Part A enrollment is automatic for beneficiaries. Declining it would generally require withdrawing from Social Security and repaying benefits received.
I already contributed after enrolling. What now?
Those are excess contributions and can be subject to tax and a penalty if left in place. They are usually corrected by withdrawing the excess and any earnings on it before your filing deadline. Speak to a tax professional, and do it sooner rather than later.
Does this apply if I only have Part A?
Yes. Part A alone is enough to end HSA eligibility.
What if I am still working past 65?
You may be able to delay Medicare and keep contributing, but it depends on employer size and whether your coverage is creditable. With fewer than 20 employees, Medicare generally pays first and delaying is usually the wrong move.
Educational disclaimer: This article provides general educational information and is not legal, tax, medical, or individualized insurance advice. HSA and Medicare rules are set by federal law and can change. Speak with a qualified tax professional about contributions, excess contributions, and qualified expenses before acting.
We do not offer every plan available in your area. Any information we provide is limited to those plans we do offer in your area. Please contact Medicare.gov or 1-800-MEDICARE to get information on all of your options. Trusted SR Solutions is not affiliated with or endorsed by the federal government or the Medicare program.