KEY POINTS
  • You can only put money in a health savings account if you are covered by a high-deductible insurance plan, which means you must stop those contributions once you're on Medicare.
  • If you accept a retroactive lump sum from Social Security because you enroll after your full retirement age and you haven't yet signed up for Medicare, your coverage will be retroactive, as well.
  • Any money paid into an HSA during that period would be considered "improper contributions" and subject to taxes.

If you regularly contribute to a health savings account and plan to claim Social Security past your full retirement age, watch out.

That's because you can no longer contribute to an HSA once you're on Medicare, no matter whether you sign up just for Part A hospital coverage (which is free) or additional parts of the program that require premiums.