Open Enrollment Is Coming. The Best Retirement Account You Own Is Probably Sitting in Cash.

Sometime in the next few weeks a benefits portal is going to open and ask you to make about six decisions in under twenty minutes. Most of them are small. One of them is not. Buried somewhere between the dental election and the life insurance you will never think about again is a question about whether you want a high-deductible health plan with a health savings account attached. Almost everyone treats that as a health insurance question. It is also, quietly, the most tax-efficient retirement account decision available to an American worker, and the evidence says hardly anyone treats it that way.

Three Tax Breaks, Which Is One More Than Anything Else Offers

Every other retirement account in the American system gives you two tax advantages at most, and makes you choose which two. A traditional 401(k) lets money in untaxed and lets it grow untaxed, then taxes every dollar that comes out. A Roth flips the order: you pay tax going in, and the growth and the withdrawals are free. Pick your poison. You are betting on where tax rates go and where your income lands, and you will not know if you guessed right for another thirty years.

A health savings account refuses to make you choose. Contributions go in before tax. Growth is untaxed. Withdrawals for qualified medical expenses come out untaxed. Three stages, no tax at any of them. That is not a loophole or an aggressive reading of the code, it is how Section 223 was written.

There is a fourth advantage almost nobody mentions. If you fund the account through payroll deduction under your employer’s cafeteria plan rather than writing a check to the custodian yourself, the money also escapes Social Security and Medicare payroll taxes. Your 401(k) does not do that. Every dollar of your 401(k) deferral still gets hit for FICA on the way past. On a full family contribution, the payroll tax savings alone are real money that simply never becomes taxable at all.

And there is a fifth. HSAs carry no required minimum distributions. Traditional IRAs and 401(k)s eventually force money out on the government’s schedule whether you need it or not. An HSA never does. After you turn 65, a withdrawal for something other than medical care is taxed as ordinary income with no penalty, which means that in the very worst case an HSA behaves exactly like a traditional IRA. In the ordinary case, where you use it for health care, it behaves better than any account you own. It is difficult to construct a scenario where it is the wrong place for a dollar you were already going to save.

What the Data Actually Shows

Here is the problem. The Employee Benefit Research Institute published a long-term study in August covering more than a decade of account activity, and the picture it paints is of a retirement account being used as a checking account. As of the end of 2024, EBRI’s database held 15.2 million accounts with about $53.7 billion in total assets. The average balance was $5,532, a record high, up from $4,747 the year before.

A record high that would not cover a single bad year. For context, the out-of-pocket maximum on an HSA-eligible plan in 2024 was roughly $8,050 for individual coverage and $16,100 for family coverage. The typical account cannot absorb one serious hospitalization, let alone fund decades of retirement health costs.

The behavior underneath explains why. Among accountholders who contributed at all, the average employee contribution was about $2,308 in 2024, well under half the statutory ceiling. Employers kicked in about $727 on average. Meanwhile 56 percent of accountholders took a distribution during the year, averaging roughly $1,870. Money goes in, money comes right back out, and the balance never gets a chance to do anything.

Then the part that should sting. Only about 18 percent of accountholders had any of their HSA invested in something other than cash. Roughly four out of five people holding the single best tax shelter in the tax code were holding it as a savings deposit. To be fair, that share has risen for eight consecutive years, and EBRI found that the longer someone has owned an account, the more likely they are to invest it and the larger the balance grows. Experience teaches. It just teaches slowly, and more than 40 percent of the accounts in the database were opened since 2022.

Why does this happen? Partly because HSAs arrive dressed as an insurance feature rather than an investment account. Nobody sits you down and explains that the thing has a brokerage window. Partly because the debit card in the envelope is an invitation to spend, and a debit card is a very effective invitation.

The Receipt Drawer

The most useful thing about an HSA is also the least advertised. There is no deadline for reimbursing yourself.

If you incur a qualified medical expense after your HSA is established, you can pay it out of your regular checking account, leave the HSA balance invested, keep the receipt, and reimburse yourself tax free years or decades later. The IRS has said as much. The expense cannot have been reimbursed by insurance or deducted on your return, and you have to keep records good enough to prove it, but there is no clock.

Think about what that means. Every medical bill you pay out of pocket becomes a tax-free withdrawal you have banked for later. A shoebox of receipts turns into a standing option to pull money out of the account without tax, at a time of your choosing, for any reason you like. The discipline it requires is unglamorous: pay small bills with cash, keep the documentation, and let the account compound.

The compounding is the whole point, and it does not require heroic assumptions. The 2026 family contribution limit is $8,750. The IRS has already set the 2027 numbers in Revenue Procedure 2026-24, raising the self-only limit to $4,500 and the family limit to $9,000, with the usual additional $1,000 for accountholders 55 and older. Contributing at the family limit for twenty years puts something close to $180,000 into the account before a dollar of growth. Whatever that money earns along the way is never taxed, provided it eventually goes toward health care.

And it will. Fidelity’s 2026 estimate puts the medical spending a single 65-year-old can expect over retirement at about $185,500, up roughly 7.5 percent from the prior year’s figure, and that number sits on top of Medicare, not instead of it. It also excludes long-term care entirely. You are going to face this expense. The only question is whether you pay for it with dollars that were taxed on the way in, on the way out, or neither.

Where the Case Gets Weaker

This is not universal advice, and anyone who presents it that way is selling something. The HSA only exists if you are enrolled in a qualifying high-deductible plan, and for 2027 that means a deductible of at least $1,750 for self-only coverage or $3,500 for a family, with out-of-pocket exposure that can run to $8,700 and $17,400 respectively. If you have a chronic condition, a family that uses care heavily, or a pregnancy on the horizon, the richer plan with the lower deductible may simply cost you less in total, and the tax advantages will not close that gap.

The invest-and-reimburse-later strategy also assumes you can afford to pay medical bills from cash you already have. If paying a $2,000 bill out of pocket means carrying it on a credit card at current rates, the tax arbitrage is a rounding error against the interest. Fix the cash cushion first.

Two other details are worth knowing. Enrolling in Medicare ends your ability to contribute, so people planning to work past 65 need to watch that timing carefully. And a small number of states, California and New Jersey among them, do not follow the federal treatment for state income tax purposes, which trims the benefit for residents there.

The Question to Ask This Fall

When the portal opens, do not just compare premiums. Ask whether your employer’s HSA custodian offers investing, what the threshold is before you can move money out of cash, and what it costs. Ask whether contributions can run through payroll so you capture the FICA break. Then decide, deliberately, whether this account is a spending account or a retirement account for you.

Most people never make that decision. They just let the default happen. The default is cash.

This article is written for educational and informational purposes only and does not constitute financial or legal advice. The views and analytical frameworks presented draw on publicly available information and reported commentary from industry participants. Readers are encouraged to consult primary sources and form their own informed views on these complex topics.