The interaction between Medicare and Health Savings Accounts (HSAs) is one of the most common—and most costly—mistakes for New Mexicans working past age 65. Enrolling in any part of Medicare (including the free Part A) immediately ends your eligibility to contribute to an HSA, and Medicare's 6-month retroactive enrollment can create tax penalties on contributions made before your application.
The 6-Month Part A Lookback Rule
When you enroll in Medicare Part A after age 65, your coverage starts up to 6 months before your application date—but no earlier than your 65th birthday month. This retroactive coverage is automatic and cannot be declined.
The HSA Problem: If you make HSA contributions during these retroactive months, the IRS treats them as ineligible contributions. You'll owe a 6% excise tax annually until you remove them, plus income tax on the contributions themselves.
What You Need to Do
- Stop HSA contributions at least 6 months before applying for Medicare. If you plan to enroll at exactly age 65, stop contributions at 64-and-6-months.
- Pro-rate your final year's contribution. If you contributed the full annual amount but only had HSA-eligible coverage for part of the year, you may owe taxes on the excess.
- Have your employer stop their HSA contributions too. Employer contributions count against your annual limit.
- You can still USE HSA funds after Medicare enrollment. You just can't contribute new money.
2026 HSA Contribution Limits
| HSA Type | 2026 Limit |
|---|---|
| Self-only coverage | $4,400 |
| Family coverage | $8,750 |
| Catch-up (age 55+) | $1,000 additional |
Strategic Considerations
If you have a high-deductible health plan with an HSA and want to maximize HSA savings, you have two main strategies:
- Delay Medicare entirely (only works if you have qualifying employer coverage from an employer with 20+ employees)
- Take Social Security at 70 instead of 65/66/67. Once you take Social Security, you're automatically enrolled in Part A and cannot opt out. Delaying Social Security keeps your HSA contributions legal.
Important: If you've already started Social Security retirement benefits, you cannot decline Part A—they're linked. Your only way to contribute to an HSA is to also withdraw from Social Security (which involves repaying past benefits).
Don't Risk an HSA Tax Penalty
The Medicare-HSA interaction has tripped up thousands of working-past-65 retirees. A licensed agent can review your specific situation and help you time enrollment properly.