In short
- From the first month you have Medicare, your HSA contribution limit is zero, including months Medicare covers retroactively.
- If you sign up 6 or more months after turning 65, stop contributions 6 months before the month you apply.
- Applying for Social Security retirement benefits also triggers Part A, with the same 6-month lookback.
- In 2026 the HSA limit is $4,400 self-only or $8,750 family, plus $1,000 at 55 and older, prorated by month in the year Medicare starts.
- You can keep spending HSA money, untaxed, on Medicare premiums and medical costs, but not on Medigap premiums.
A Health Savings Account (HSA) and Medicare do not mix: once any part of Medicare starts, you can no longer put money into an HSA. The trap is timing. When you sign up for Medicare after 65, Part A is usually backdated up to 6 months, which can turn contributions you already made into excess contributions. Medicare's advice is to stop contributing 6 months before you apply.
This is not tax advice. It is how the Medicare and IRS rules fit together, so you can ask the right questions of your HR department and tax preparer.
Why can't you contribute to an HSA once you have Medicare?
To contribute to an HSA, you must be covered by a qualifying high-deductible health plan and have no other disqualifying coverage. Medicare counts as other coverage. IRS Publication 969 says: "Beginning with the first month you are enrolled in Medicare, your contribution limit is zero." That applies to Part A alone, and it applies to retroactive Medicare coverage too.
It also applies to your employer's contributions. Medicare.gov's working past 65 page says "you and your employer should stop contributing to your HSA 6 months before you retire or apply for benefits from Social Security."
The money already in your HSA stays yours. You just cannot add more.
How does the 6-month Part A lookback work?
Part A with no premium goes back (retroactively) 6 months from the month you sign up for Part A or apply for Social Security or Railroad Retirement benefits. It never goes back earlier than the first month you were eligible for Medicare, usually the month you turned 65.
That backdating is normally a good thing, because it can cover a hospital stay you had before you applied. For HSA owners, it means up to 6 months of contributions can land in months when you technically had Medicare.
Two common ways people trigger Part A without realizing the HSA effect:
- Applying for Social Security retirement benefits. You are enrolled in Part A automatically, and you cannot decline it while collecting benefits. Social Security's policy is that the only way out is to withdraw your application and repay all benefits received.
- Signing up for Part A "just because it has no premium." Fine for most people. Not fine if you are still funding an HSA.
When should you stop HSA contributions?
Medicare & You 2027 gives this guide:
| When you sign up for Medicare | Make your last HSA contribution |
|---|---|
| During your Initial Enrollment Period | The month before you turn 65 |
| During your Initial Enrollment Period, birthday on the 1st | 2 months before you turn 65 |
| Less than 6 months after you turn 65 | The month before you turn 65 |
| 6 or more months after you turn 65 | 6 months before the month you apply |
If your employer deposits HSA money through payroll, give HR your stop date in writing well ahead of time. Payroll systems often keep contributing until someone changes the election.
Worked example: retiring at the end of 2026
Carol turned 65 in March 2025. She is still working at a Lincoln company with 150 employees, has self-only coverage through its HSA-qualified plan, and contributes the 2026 maximum by payroll. She plans to retire on December 31, 2026, and apply for Medicare and Social Security in December 2026.
- Part A backdates 6 months from December 2026, to June 1, 2026. That is later than March 2025, so the full 6 months apply.
- Her last HSA-eligible month is May 2026. From June 2026 on, her contribution limit is zero.
- Her 2026 limit is prorated. The 2026 limit is $4,400 for self-only coverage plus a $1,000 catch-up at 55 or older, $5,400 in all. Eligible for 5 of 12 months: $5,400 x 5 / 12 = $2,250.
- If payroll kept going all year, she would have put in up to $5,400, leaving up to $3,150 in excess contributions, which face a 6% excise tax each year they stay in the account unless withdrawn by her tax filing deadline.
The fix is simple if she plans ahead: stop HSA contributions after May 2026, or apply for Medicare earlier and stop the month before Part A starts. If you are in Carol's spot and it is already October, talk to your HSA custodian and tax preparer now about removing any excess.
What if you already over-contributed?
Contributions made in months you had Medicare are excess contributions. According to IRS Publication 969, excess contributions are subject to a 6% excise tax for each year they remain in the account. You can avoid that tax by withdrawing the excess, plus any earnings on it, by the due date of your tax return, including extensions. The earnings are taxable income.
Ask your HSA custodian for its excess contribution removal form, and tell your tax preparer.
Can you delay Medicare to keep funding your HSA?
You can, if three things are true:
- You are covered by a group plan from current employment at an employer with 20 or more employees, so it pays first.
- You are not collecting Social Security retirement benefits.
- Your employer's drug coverage is creditable, so you will not owe a Part D penalty later.
Then you can delay Part A and Part B without penalties and sign up during the 8-month Special Enrollment Period after the job or coverage ends. Remember the 6-month lookback when you do apply. The full rules are in working past 65 and employer coverage vs Medicare.
Can you still use your HSA after Medicare starts?
Yes, and it becomes very useful. After 65, IRS Publication 969 lets you spend HSA money without tax on:
- Part B premiums (including the standard $202.90 a month in 2026)
- Part D and Medicare Advantage premiums
- Deductibles, copays and coinsurance, like the $1,736 Part A deductible or the $283 Part B deductible in 2026
- Dental, vision and hearing costs that Medicare does not cover
- Qualified long-term care insurance premiums, up to IRS limits
The one exception: Medigap premiums are not a qualified expense. If you buy a Medigap policy, pay its premium from other money.
Higher income while you work can also raise your Medicare premiums two years later through IRMAA. For the full timeline around your birthday, see the turning 65 checklist and Medicare Part A.
Questions about Medicare start dates go to Social Security at 1-800-772-1213 or 1-800-MEDICARE (1-800-633-4227), available 24 hours a day, 7 days a week (TTY 1-877-486-2048). Nebraska SHIP (1-800-234-7119) also counsels at no cost. HSA tax questions belong with a tax professional. When you are ready to pick coverage, talk to Bill.
Frequently asked questions
No. The IRS rule is that your HSA contribution limit drops to zero beginning with the first month you are enrolled in Medicare, and Part A counts. That includes your employer's contributions. If you want to keep contributing while you work past 65, you would need to delay both Part A and Part B, which also means not starting Social Security retirement benefits yet.
When you sign up for Part A after 65, or apply for Social Security, Part A with no premium is backdated up to 6 months, but no earlier than the month you turned 65. Any HSA contributions made during those backdated months become excess contributions. Stopping 6 months before you apply means none of your contributions land in a month Medicare covers.
Those contributions are excess contributions. The IRS charges a 6% excise tax on excess contributions for each year they stay in the account. You can avoid the tax by withdrawing the excess, and any earnings on it, by your tax return due date including extensions. Ask your HSA custodian for an excess contribution removal and talk with a tax professional.
Yes, once you are 65. IRS Publication 969 lists Medicare and other health coverage premiums as qualified expenses for people 65 or older, which covers Part B, Part D and Medicare Advantage premiums. Medigap premiums are specifically excluded. You can also use HSA money, untaxed, for deductibles, copays, coinsurance, dental and vision costs, and some long-term care insurance premiums.
Sometimes. If you are covered by a current employer's plan at a company with 20 or more employees and you are not collecting Social Security, you can delay Part A and Part B without penalties. Your employer's drug coverage must be creditable to avoid a Part D penalty. If the employer has fewer than 20 employees, Medicare pays first, so delaying Part B is risky.
Sources
- IRS Publication 969: Health Savings Accounts (opens in a new tab)
- Medicare & You 2027 handbook (CMS Product 10050), page 20 (opens in a new tab)
- Medicare.gov: Working past 65 (opens in a new tab)
- SSA POMS HI 00801.002: Waiver of Part A entitlement (opens in a new tab)
- Medicare.gov: When does Medicare coverage start? (opens in a new tab)
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. 1-800-MEDICARE (1-800-633-4227) is available 24 hours a day, 7 days a week. TTY users can call 1-877-486-2048.
