The 6-month Part A lookback rule
When you enroll in Medicare Part A, coverage can be retroactive up to 6 months. This is important because IRS rules say you cannot contribute to an HSA for any month you are enrolled in Medicare.
What this means: If you plan to enroll in Part A, you must stop HSA contributions at least 6 months before your Part A effective date. Otherwise, you could face IRS tax penalties on those contributions.
Your options at 65
Option 1: Delay Part A and keep the HSA. If you work for a large employer (20+), you can delay both Part A and Part B. This lets you keep contributing to your HSA and keep the tax benefits. You'll enroll in Medicare when you retire.
Option 2: Enroll in Part A and stop HSA contributions. Since Part A is free for most people, some choose to enroll in Part A at 65 for the added hospital coverage. But you must stop HSA contributions 6 months before your Part A start date.
Using existing HSA funds
Even after you enroll in Medicare, you can still use existing HSA funds tax-free for qualified medical expenses, including Medicare premiums, deductibles, copays, and coinsurance. You just can't make new contributions.
Colorado-specific HSA considerations
Colorado follows federal tax treatment of HSAs. There are no additional state-level complications. However, if you're a federal employee at facilities like the Denver Federal Center or NOAA, your FEHB plan may have specific HSA coordination rules worth reviewing.
HSA + Medicare timeline
| Action | When |
|---|---|
| Stop HSA contributions | 6 months before Part A starts |
| Enroll in Part A (if desired) | At 65 or at retirement |
| Enroll in Part B | At 65 or during 8-month SEP after retirement |
| Use remaining HSA funds | Anytime — no deadline |