HSAs and Medicare: Contributions, the 6-Month Rule, and Paying Premiums

The Core Rule: Medicare Ends HSA Contributions

A Health Savings Account is paired with a qualifying high-deductible health plan (HDHP). To contribute, IRS rules require that you have no other disqualifying coverage — and Medicare counts as disqualifying coverage. Beginning with the first month you are enrolled in any part of Medicare (Part A, Part B, Part C, or Part D), your HSA contribution limit is zero.

This is enrollment-based, not age-based. Turning 65 does not by itself stop your eligibility — many people work past 65, keep their employer HDHP, and delay Medicare so they can keep contributing. What ends contributions is actually being enrolled in Medicare, including the premium-free Part A that many people are auto-enrolled into when they claim Social Security.

Important: the account itself does not disappear. You keep every dollar already in your HSA, it continues to grow tax-free, and you can spend it tax-free on qualified medical expenses for the rest of your life. Only new contributions stop.

The 6-Month Lookback Trap

This is the rule that catches the most people. When you enroll in premium-free Part A after age 65 — or when you start Social Security retirement benefits, which triggers automatic Part A — your Part A coverage is backdated up to 6 months (but no earlier than your 65th birthday month).

Because of that retroactive start date, any HSA contributions you (or your employer) made during those backdated months become excess contributions, even though Medicare wasn't on your radar yet when you made them.

Medicare's own guidance is direct: to avoid a tax penalty, you and your employer should stop contributing to your HSA at least 6 months before you apply for Medicare or for Social Security/Railroad Retirement Board benefits. Plan your final contribution around that 6-month window — not around your enrollment date.

• The lookback only applies once you are past 65 and actually enrolling; it never reaches back before the month you turned 65.
• Employer contributions count too — tell your benefits administrator when you plan to stop.
• Excess contributions left in the account are generally subject to a 6% excise tax each year until corrected.

2026 HSA Contribution Limits

If you are still HSA-eligible (no Medicare, covered by a qualifying HDHP), these are the IRS limits for the 2026 tax year, set by Revenue Procedure 2025-19:

If Medicare starts partway through the year, your contribution limit is prorated — you can generally contribute for the months before Medicare began. Form 8889 walks through the month-by-month calculation, and a tax professional can confirm your exact figure.

• Self-only HDHP coverage: $4,400
• Family HDHP coverage: $8,750
• Catch-up contribution, age 55 and older: an extra $1,000 (a fixed statutory amount)
• To qualify, the HDHP must have a deductible of at least $1,700 self-only / $3,400 family, with out-of-pocket maximums no higher than $8,500 self-only / $17,000 family

Using HSA Funds to Pay Medicare Costs

Even though you can't contribute once you're on Medicare, your existing HSA becomes a powerful tool for paying Medicare expenses tax-free. Once you are 65 or older, you can withdraw HSA money tax-free to pay most Medicare premiums — a benefit not available for most other insurance premiums.

Withdrawals for non-qualified expenses are still allowed after 65 but are taxed as ordinary income (the extra 20% penalty no longer applies at that age). Keep receipts: you, not the HSA custodian, are responsible for proving a withdrawal was for a qualified expense.

• Qualified tax-free: Part B premiums (e.g., the standard $202.90/month in 2026), Part D drug-plan premiums, and Medicare Advantage (Part C) premiums.
• Qualified tax-free: Part A premiums, if you're among the minority who must pay them, plus deductibles, copays, and coinsurance under any part of Medicare.
• NOT qualified: Medicare Supplement (Medigap) premiums — IRS rules specifically exclude Medigap from the tax-free premium list.
• Reimbursement of any IRMAA high-income surcharge added to your Part B or Part D premium is generally treated the same as the underlying premium.

A Practical Timing Checklist

• Working past 65 with an HDHP and want to keep contributing? You can — but only if you delay all parts of Medicare, including premium-free Part A, and do not claim Social Security.
• Claiming Social Security automatically enrolls you in Part A; plan your last HSA contribution for at least 6 months before that.
• Decide your Medicare start date first, then count back 6 months to set your final contribution month.
• Switching to spend-down mode? Save Medicare premium notices and medical receipts so every tax-free withdrawal is documented.
• Rules interact with employer size, COBRA, and spousal coverage — confirm your specific situation with a tax advisor or benefits administrator before your 65th birthday.