HSAs and Medicare: the six-month lookback that catches people out
Why enrolling in Medicare ends HSA contributions, how Part A's retroactive coverage creates tax penalties, and how to plan the last contribution.
A Health Savings Account is a strong tax shelter, but you cannot contribute once you enroll in any part of Medicare.
The retroactive trap
When you sign up for premium-free Part A after 65, coverage is backdated up to six months (but not before 65). Contributions made in those months are excess contributions and face a 6% excise tax unless withdrawn.
Rule of thumb: stop HSA contributions six months before you apply for Medicare (if over 65), and prorate the contribution in your final year.
Claiming Social Security enrolls you in Part A
If you start Social Security after 65, Part A starts automatically and is backdated. Plan HSA contributions before you file.
You can still spend the HSA
Existing HSA money can pay tax-free for Medicare premiums (Parts B and D, Medicare Advantage, but not Medigap premiums), deductibles, copays and other qualified expenses.
Related: when to delay Part B and Medicare's 2026 costs.
Questions people ask
Can I contribute to an HSA on Medicare?
No. Contributions must stop when any part of Medicare starts.
What is the six-month lookback?
Part A is backdated up to six months when you enroll after 65.
Can HSA money pay Medigap premiums?
No, but it can pay Part B, Part D and Medicare Advantage premiums.
Does claiming Social Security start Part A?
Yes, if you are 65 or older.
Independent educational site. Not affiliated with or endorsed by the U.S. government, the federal Medicare program, or any insurance company. Figures are 2026 amounts published by CMS unless noted; check Medicare.gov for your situation.