HSA Pre-Medicare

The HSA-Medicare interaction has two surprises that bite people who have otherwise done everything right.

Surprise one: any Medicare enrollment — including premium-free Part A — disqualifies you from contributing to an HSA. If you're 65 and still have employer coverage you'd like to keep contributing to your HSA from, you generally need to delay all parts of Medicare, including Part A. That's a non-obvious consequence of the rule "Medicare enrollment ends HSA contributions."

Surprise two: when you eventually sign up for Medicare past 65, Social Security can backdate Part A by up to six months from your application date. That backdating creates a window of months in which you contributed to an HSA while retroactively enrolled in Part A — which can disqualify those contributions and trigger an excess-contribution penalty unless you correct them.

This category covers the HSA-Medicare disqualification rule, the six-month retroactive Part A trap, the strategy of stopping HSA contributions a few months before the Medicare application, and how the HSA-Medicare timing interacts with the SEP for ending employer coverage.