Working Past 65: The Earnings Test, Medicare Timing, and the HSA Trap

A guy named Tom — Dartmouth retired plumber, but he kept consulting on the side after his "official" retirement at 64 — came to a workshop a couple months ago with a question that gets to the heart of this article. "Matt, I'm 66. I'm still working about 30 hours a week. Do I sign up for Medicare? Do I take Social Security? My HSA at the consulting client has been getting funded — is that still legal? Nobody at the office knows." Right? Three rules. Three different parts of the federal government. Three sets of consequences if you get them wrong. And it turns out almost nobody gets a clean explanation of how they interact. Let me walk you through them.

The three rules are: the Social Security earnings test, the Medicare enrollment timing rules, and the HSA-and-Medicare conflict. Tom needed all three explained at once because they all activate at the same age and they all interact. Here we go.

Rule 1: The Social Security Earnings Test

If you claim Social Security before your Full Retirement Age (which is 67 for anyone born in 1960 or later) and you keep working, the Social Security Administration applies an "earnings test" to your benefits. The earnings test withholds part of your benefit if your earned income — wages from employment, net self-employment earnings — exceeds certain limits.

Here's the part most people miss. Withheld benefits are not lost. Once you reach FRA, the Social Security Administration recalculates your benefit and credits the withheld amounts back to you in the form of higher monthly checks for the rest of your life. So the earnings test isn't a tax — it's a deferral.

Tom is 66 and his FRA is 67. If he claims SS now while still earning, say, $45,000 a year from consulting, the math works like this: he's $20,520 over the $24,480 limit, so SSA would withhold $10,260 of his annual benefit. If his benefit was supposed to be $24,000 a year, he'd actually receive $13,740 in 2026. Then in 2027 — his FRA year — until the month he turns FRA, the higher $65,160 threshold applies. After his FRA birthday, no withholding at all.

The strategic question for Tom: should he claim now, knowing the earnings test will withhold most of the benefit (which gets credited back later as a higher monthly check)? Or should he wait until FRA when he can collect the full benefit immediately AND avoid early-claiming reductions? For most people working past 62, the answer is "wait until FRA at the earliest, ideally to 70 if longevity and spouse situation support it." The earnings test alone is rarely a reason to claim earlier — but it is a reason not to claim earlier and assume you'll get the full check.

Rule 2: Medicare enrollment when you have employer coverage

Most pre-retirees enroll in Medicare during their seven-month Initial Enrollment Period (IEP) — three months before their 65th birthday month, the birthday month itself, and three months after. Miss that window without alternative coverage and you face a lifetime late-enrollment penalty on Part B (10% of the standard premium for every 12-month period delayed).

The exception that matters for working pre-retirees: if you have creditable employer-sponsored coverage from an employer with 20 or more employees, you can delay Medicare Part B without penalty until that coverage ends. You then have an 8-month Special Enrollment Period to sign up after your employment or coverage ends.

Two important caveats:

• The "20 or more employees" rule matters. Smaller employers (under 20) generally make Medicare primary at 65, meaning you should enroll in both Part A and Part B at 65 even if you have employer coverage. Confirm with your employer's HR that the plan is treated as primary.
• "Creditable coverage" is a defined term. Most large-employer group health plans qualify. Some don't. Get the determination in writing if you're going to rely on it.

For Tom, this is where it gets interesting. He's not covered by an employer health plan — he's a consultant, working as a 1099 contractor, no group coverage. So the "delay Part B because I have employer coverage" exception doesn't apply to him. He should have enrolled in Medicare at 65 during his IEP. If he didn't, he's potentially facing a late-enrollment penalty when he eventually does enroll.

Rule 3: The HSA-and-Medicare conflict

This is the trap most pre-retirees walk into without realizing it. Once you are enrolled in any part of Medicare — including Part A by itself — you can no longer contribute to a Health Savings Account. Your existing HSA balance can stay where it is and be used for qualified medical expenses (it doesn't go away), but new contributions must stop.

The brutal twist: when you claim Social Security at any point past 65, you are automatically enrolled in Medicare Part A, retroactively up to six months. So if you've been making HSA contributions in the months before claiming SS, those contributions are now considered excess contributions. The IRS imposes a 6% excise tax on excess HSA contributions for every year they remain in the account.

Tom's situation: he has an HSA from the consulting client and has been contributing $4,000 a year. If he claims Social Security at 67, the retroactive Part A enrollment applies. If he made HSA contributions in the six months before his Social Security claim, those contributions are excess and he owes the excise tax.

The fix is straightforward but has to be intentional:

• If you want to keep contributing to an HSA, delay Social Security past your 65th birthday. Specifically, delay it long enough that the 6-month retroactive Part A doesn't reach back into months when you were contributing.
• If you're already enrolled in Part A (automatic if you collected SS at 65), stop HSA contributions from that month forward. Existing balance is fine; new contributions are not.
• Use existing HSA balance for medical expenses tax-free at any age. The balance is yours forever. Just stop adding to it once you're on Part A.

The HSA contribution limit in 2026 is approximately $4,300 individual / $8,650 family, plus a $1,000 catch-up for age 55+. Losing the ability to contribute is meaningful — these are some of the most tax-advantaged dollars in the U.S. tax code (deductible on the way in, growth-tax-free, withdrawable tax-free for medical expenses). For pre-retirees who plan to keep working past 65 with HDHP coverage, the HSA-and-Medicare timing is its own planning conversation.

How the three rules interact

Here's where Tom's situation got complicated. He had three decisions and they were all linked:

• If he claimed Social Security now at 66, the earnings test would withhold most of his benefit and the retroactive Part A enrollment would kill his HSA contributions.
• If he delayed Social Security to 67 or 70, his benefit would grow with delayed retirement credits, and he could keep his HSA contributions intact (assuming he didn't enroll in Part A separately).
• His Medicare enrollment was already a question because he hadn't enrolled at 65 — he should verify whether his consulting income generated any creditable coverage option (it didn't), confirm his late-enrollment exposure, and enroll during the next available window.

The integrated answer for Tom: delay Social Security to 70 (his health and spouse situation supported it), enroll in Medicare Part A and Part B during the next general enrollment period (accepting a small late-enrollment penalty), and stop HSA contributions effective when Part A activates. Mixed result — he had a small Medicare penalty he could have avoided, but the SS delay strategy more than offset it.

The four-step decision framework for working pre-retirees

• Confirm whether you have creditable employer coverage. If yes (and the employer is 20+ employees), you can defer Part B without penalty. If no, plan to enroll at 65.
• Decide your Social Security claim age based on overall strategy — health, spouse, longevity, tax — not just whether you're working. The earnings test is a wrinkle, not a determining factor.
• If you want to keep contributing to an HSA, delay Social Security long enough to avoid the 6-month retroactive Part A enrollment reaching back into HSA-contribution months.
• Coordinate the three decisions. Don't claim Social Security at 65 by default if you're still working with an HSA; don't ignore Medicare enrollment if you don't have qualifying employer coverage.

What this looks like in practice

Working past 65 is a great choice for plenty of people — meaningful work, social connection, financial cushion, mental engagement. But the federal rules around Social Security, Medicare, and HSAs all activate at 65 and don't coordinate well unless you make them. The penalty for getting it wrong isn't enormous — usually a Medicare late-enrollment penalty in the hundreds of dollars per year, or an HSA excise tax in the low hundreds — but it adds up over a long retirement and feels punitive when you discover you stepped on a rake nobody told you about.

The best version of this conversation happens 12 to 18 months before your 65th birthday — when you can plan the timing intentionally instead of reacting to a missed deadline. Sleep at night, knowing the three rules are coordinated.

The bottom line

If you're working past 65, three federal rules activate at the same time and don't coordinate themselves. The earnings test withholds Social Security benefits if you claim before FRA and earn too much (but credits them back at FRA). Medicare enrollment can be deferred if you have creditable employer coverage from a 20+ employer; otherwise, late-enrollment penalties are permanent. HSA contributions must stop when any Part of Medicare begins, and the 6-month retroactive Part A from claiming Social Security past 65 can create excess HSA contributions if you weren't paying attention. Coordinate the three decisions before your 65th birthday — not after.