The HSA-Medicare Conflict
If you have a Health Savings Account (HSA) and approach 65, you face a critical decision. Once you enroll in any part of Medicare — including premium-free Part A — you can no longer contribute to an HSA. This catches many California workers off guard, particularly those at tech companies and large employers with HSA-compatible high-deductible health plans.
The 6-Month Lookback Rule
When you enroll in Medicare or claim Social Security at age 65 or later, Part A coverage is retroactive up to 6 months (but no earlier than your 65th birthday month).
This means HSA contributions made during those 6 retroactive months are technically excess contributions — subject to taxes and a 6% excise tax penalty unless withdrawn before your tax deadline.
How to Avoid the HSA Penalty
- Stop HSA contributions 6 months before enrolling in Medicare. If you plan to enroll at 65, stop contributions at 64.5.
- Don’t claim Social Security before 65 if you want to keep contributing to your HSA. Claiming Social Security automatically enrolls you in Part A.
- Pro-rate your annual contribution based on the number of months you’re HSA-eligible.
You Can Still USE Your HSA After Medicare Enrollment
The rule only prohibits new contributions. You can continue to:
- Pay for qualified medical expenses tax-free with existing HSA funds
- Pay Medicare premiums (Part B, Part D, Medicare Advantage) with HSA funds tax-free
- Pay for long-term care insurance with HSA funds
Strategy for Workers Who Want to Keep Contributing
If you’re 65+ and still working with HSA-compatible coverage, you can decline Medicare enrollment entirely (including Part A) and continue HSA contributions. But this requires being eligible to delay — your employer must have 20+ employees and you should not be receiving Social Security benefits.