If you have a Health Savings Account through your employer or self-employment, turning 65 and signing up for Medicare changes the rules. Once you are on Medicare, you can no longer contribute new money to an HSA. The rules are not always obvious, and the wrong move can cost you tax penalties. Here is what to know.
What is a Health Savings Account?
A Health Savings Account (HSA) is a tax-advantaged account you can use for medical expenses. To contribute to one, you must be enrolled in a qualified high-deductible health plan (HDHP) and meet a few other requirements.
HSAs have three tax breaks. Contributions are pre-tax. Money in the account grows tax-free. Withdrawals for qualified medical expenses are tax-free. It is one of the best tax-advantaged accounts available.
The basic rule: no HSA contributions on Medicare
Once you enroll in any part of Medicare, including just Part A, you can no longer contribute new money to an HSA. This is a hard IRS rule.
You can still use the money already in your HSA for qualified expenses. You just cannot add new contributions for the months you are on Medicare.
The 6-month look-back trap
This is where most people get tripped up. When you enroll in Medicare Part A after age 65, Medicare gives you 6 months of retroactive coverage.
That means if you sign up for Medicare in July, your Part A coverage actually starts in January (6 months back). For HSA purposes, you are technically on Medicare for those 6 retroactive months.
So you cannot contribute to your HSA for those 6 months. If you did contribute during that window, the IRS treats those contributions as excess and you owe a 6 percent excise tax plus income tax on the amount.
How the look-back affects timing
The look-back can never go back farther than your 65th birthday. So if you delay Medicare past 65 and keep contributing to your HSA, you must stop contributing at least 6 months before you sign up for Medicare.
Example: You want to stop contributions December 31, 2027. You can apply for Medicare no earlier than July 1, 2028. If you apply earlier, the retroactive coverage will hit some of your 2027 contributions.
What if I keep working and want to delay Medicare?
Many people work past 65 and want to keep contributing to their HSA. You can do this, but only if both of these are true:
- You have employer health coverage from a company with 20 or more employees (so you can delay Part B with no penalty)
- You delay enrolling in Medicare entirely, including Part A
Most people enroll in Part A at 65 because it is free and seems like there is no downside. But if you have an HSA, signing up for Part A locks you out of contributions.
For more on working past 65, see our guide on employer coverage.
If you take Social Security, you cannot delay Part A
One catch: if you start collecting Social Security at or after 65, you are automatically enrolled in Medicare Part A. You cannot decline it. So you cannot keep contributing to an HSA.
The only way to delay Medicare Part A is to also delay Social Security. If you want to keep contributing to your HSA past 65, you need to hold off on Social Security too.
Using existing HSA money for Medicare expenses
You can use existing HSA money for many Medicare costs tax-free. Qualified expenses include:
- Medicare Part B premiums
- Medicare Part D premiums
- Medicare Advantage premiums (but not Medigap premiums)
- Copays, deductibles, and coinsurance
- Long-term care insurance premiums (up to age-based limits)
- Most out-of-pocket medical expenses, including dental and vision
This makes the HSA a powerful tool for retirement healthcare planning. The money you saved tax-free can pay your Medicare expenses tax-free.
One thing HSAs do NOT cover
Medigap premiums are not a qualified HSA expense. This is a strange IRS rule. Most other Medicare-related premiums work, but Medigap does not.
If you want to use HSA money for your supplement, you would pay the premium with after-tax money. Medicare Advantage premiums are fine.
Strategies for HSAs near 65
Strategy 1: Stop contributing 6 months before Medicare
If you plan to sign up for Medicare on time at 65, stop HSA contributions during the month you turn 64.5. This avoids the look-back excise tax.
Strategy 2: Delay Medicare to keep contributing
If you have qualified employer health coverage and a strong HSA, delay Medicare entirely. Keep contributing until you finally enroll. This requires not taking Social Security too.
Strategy 3: Front-load contributions
In your final HSA year, contribute the maximum you can while still working. Most people in their 60s also get a $1,000 catch-up contribution. Take advantage.
Strategy 4: Spousal HSA
If you are on Medicare but your spouse is not, your spouse can still contribute to their own HSA. Just remember the HSA must be in their name and based on their coverage, not yours.
HSA penalties to avoid
The big one: contributing to an HSA after you are on Medicare. The penalty is 6 percent of the excess contribution per year, every year, until you remove it. Plus you owe income tax on the contribution.
If this happened to you, talk to your HSA custodian about removing the excess contribution. The deadline is generally the tax filing deadline (April 15 of the following year).
What to do at 65
Here is a simple 4-step plan:
- Six months before you turn 65, decide if you are taking Medicare on time or delaying.
- If taking on time, stop HSA contributions for the months that the look-back will hit.
- If delaying, confirm your employer plan is qualified (20+ employees) and decide not to take Social Security yet either.
- Use your existing HSA balance strategically to pay Medicare premiums, copays, and other qualified expenses in retirement.
Talk to a pro
The HSA and Medicare interaction is one of the most missed topics in retirement planning. Most financial advisors and HR departments do not know the look-back rule. If you have a substantial HSA and are turning 65, talk to a CPA or tax advisor who understands these rules before you sign up for Medicare.
A Medicare agent can help with the Medicare side, but HSA rules are IRS territory. The right move is to coordinate with both.
