Can You Contribute to an HSA After 65? Medicare Backdating and Penalties

You can contribute to an HSA after 65, but only for months in which you are not enrolled in any part of Medicare. The moment Medicare coverage begins — Part A, Part B, Part D, or Medicare Advantage — your contribution limit drops to zero for every month you are covered. For 2026, the annual limit is $4,400 for self-only HDHP coverage or $8,750 for family coverage, plus a $1,000 catch-up if you are 55 or older.¹ Your existing balance stays yours to spend tax-free on qualified medical expenses no matter what.

Turning 65 Does Not End HSA Eligibility. Medicare Does

The birthday itself changes nothing. What ends your ability to contribute is enrollment in Medicare. If you have not signed up for any part of Medicare and still have HDHP coverage, you can keep contributing exactly as you did before.²

The complication is Part A. Most people qualify for premium-free Part A based on their work record, and because it costs nothing, many assume they have to take it. You do not. You can decline Part A at 65 and stay HSA-eligible — but only if you have not started collecting Social Security. Once Social Security payments are flowing, enrollment in Part A is automatic at 65 and cannot be refused.³ If you started Social Security before 65, both Part A and Part B are activated automatically on the first day of the month you turn 65.⁴

Preserving HSA eligibility past 65 therefore requires delaying two things: Medicare enrollment and Social Security benefits.

Contributing While Still Working

If you are working past 65 and your employer offers an HDHP, you can keep contributing indefinitely as long as you stay off Medicare and Social Security. Whether that is a good deal depends partly on your employer’s size.

When your employer, or your spouse’s employer, has 20 or more employees, the group health plan pays first and Medicare would pay second if you were enrolled.⁵ At employers with fewer than 20 employees, Medicare pays first and the employer plan becomes secondary.⁶ Either way, enrolling in any part of Medicare ends HSA contributions. But workers at smaller companies may find their employer coverage less protective on its own, which makes the trade-off harder.

The Part B Late Enrollment Penalty

Delaying Medicare to keep contributing has a real risk on the other end. If you postpone Part B without qualifying employer coverage, Medicare adds 10% to your monthly Part B premium for every full 12 months you could have enrolled and did not. That surcharge is permanent. Three years of delay means a 30% premium bump for life.⁷

The way through is the Special Enrollment Period. If you had group health coverage through your own or your spouse’s current employment, you get an eight-month window after that employment or the coverage ends to sign up for Part B with no penalty.⁸ Miss the window and you may face both the lifetime surcharge and a wait for the next General Enrollment Period, which runs January 1 through March 31.

The Six-Month Backdating Trap

This is the rule that catches the most people. When you apply for Part A, or for Social Security, more than six months after turning 65, your Part A coverage is backdated up to six months from your application date (never earlier than the month you turned 65).⁹

Any HSA contributions you made during those retroactively covered months become excess contributions. The IRS treats you as having been on Medicare when the deposit hit, even though you did not know it at the time.² Apply for Social Security in December with a July backdate, and every contribution from July through December is excess, exposed to a 6% excise tax each year it stays in the account.

The clean fix is to stop HSA contributions at least six months before you plan to file for Social Security or Medicare. That buffer covers the maximum backdating window, so no contributions overlap with retroactive Medicare coverage.

Pro-Rating in the Year You Enroll

If you sign up for Medicare partway through a year, your annual limit is pro-rated to the months you were eligible. Take the annual limit including any catch-up, divide by 12, multiply by the number of months before Medicare began.²

Say you turn 65 in July 2026 and enroll in Medicare that month, with self-only HDHP coverage for January through June. Your combined limit — $4,400 plus the $1,000 catch-up — is $5,400. Divided by 12 and multiplied by six eligible months, your ceiling for the year is $2,700. Anything above that is excess.

When One Spouse Goes on Medicare

HSAs are individually owned; there is no joint HSA even for couples on the same plan.² One spouse enrolling in Medicare does not disqualify the other. The still-eligible spouse can keep contributing on their own account, and if they carry family HDHP coverage, they can contribute up to the family limit.

The total across both spouses’ HSAs for the year still cannot exceed the family maximum. Couples can split it however they agree; absent an agreement, the IRS divides it evenly.¹⁰ Whatever the newly-enrolled spouse already contributed earlier in the year counts against that shared family cap.

Catch-up contributions work differently. Each spouse aged 55 or older who is not on Medicare gets their own $1,000 catch-up, and it has to go into that spouse’s own HSA. You cannot deposit a catch-up into your partner’s account.

Fixing an Excess Contribution

If you contributed during a month you were actually on Medicare — whether from backdating, automatic enrollment, or a missed calculation — the excess amount is hit with a 6% excise tax for every year it remains in the account. The tax is figured on the lesser of the excess or the HSA’s December 31 value.²

To avoid the penalty, withdraw the excess plus any earnings it generated before the due date of your federal return, extensions included.² For 2026 contributions, that is generally April 15, 2027, or October 15, 2027 with an extension. The withdrawn earnings get reported as income for the year of the withdrawal.¹¹ If you miss the correction deadline, the 6% tax gets reported on Form 5329 and keeps accruing until the excess is gone.¹²

Spending the Balance After 65

Losing the ability to contribute does not restrict how you spend what is already in the account. Qualified medical expenses stay tax-free at any age.²

Once you turn 65, the list of premiums you can pay tax-free from an HSA expands. Medicare Part A premiums (if you owe one), Part B, Part D, and Medicare Advantage premiums all qualify. Medigap premiums do not — that exclusion is written into the statute.¹³

Non-medical withdrawals also change at 65. Before then, they trigger income tax plus a 20% penalty. After 65, the 20% penalty is gone; you owe only ordinary income tax, similar to a traditional retirement account.² That flexibility is why many people treat an HSA as a supplemental retirement account — spent tax-free on health costs first, and available as taxable income for anything else.

1
Internal Revenue Service. IRS Notice 2026-05, Expanded Availability of Health Savings Accounts
2
Internal Revenue Service. Publication 969 (2025), Health Savings Accounts and Other Tax-Favored Health Plans
3
Social Security Administration. When to Sign Up for Medicare
4
Social Security Administration. Medicare
5
Medicare. How Medicare Works with Other Insurance
6
Centers for Medicare and Medicaid Services. Medicare Secondary Payer
7
Medicare. Avoid Late Enrollment Penalties
8
Social Security Administration. How to Apply for Medicare Part B During Your Special Enrollment Period
9
Medicare. When Does Medicare Coverage Start
10
Internal Revenue Service. Rules for Married People
11
Internal Revenue Service. Instructions for Form 8889 (2025)
12
Internal Revenue Service. Form 5329, Additional Taxes on Qualified Plans and Other Tax-Favored Accounts
13
Office of the Law Revision Counsel. 26 USC 223 – Section: Definitions and Special Rules