The HSA, the most tax-advantaged account most people ignore

A Health Savings Account is the only account in the tax code that gives you three breaks at once. Money goes in before tax, so it lowers this year's taxable income. It grows tax-free while it sits invested. And it comes out tax-free when you spend it on a qualified medical cost. A 401(k) gives you two of those at best. A Roth IRA gives you two. The HSA gives you all three, and almost nobody under 30 uses it for what it can actually do.

Who can open one

There is one gate: you need a high-deductible health plan (HDHP). For 2025 that means a plan with a deductible of at least $1,650 for an individual or $3,300 for a family, and out-of-pocket limits the IRS caps each year. If your employer offers an HDHP, you almost certainly have an HSA option sitting next to it during open enrollment. If your plan has a low deductible and copays for everything, you do not qualify, and no HSA for you this year.

That single requirement is why so many young people skip it. The HDHP scares people off because the deductible looks big. But if you are healthy and rarely see a doctor, the lower monthly premium on an HDHP often beats the richer plan, and the HSA you get alongside it is the real prize.

The 2025 limits

You can put in $4,300 as an individual or $8,550 for family coverage in 2025. If you are 55 or older you can add another $1,000 catch-up. Contributions made through payroll skip federal income tax and FICA, which is a perk a Roth IRA or a regular IRA does not give you. Money you add on your own later is deductible on your return, so you still get the break, you just claim it at tax time instead of on your paycheck.

The move most people miss: invest it, do not spend it

Most people treat the HSA like a checking account for the dentist. They put money in, swipe the debit card, and the balance hovers near zero. That works, and it still saves you the tax on every medical dollar. But it wastes the best feature.

Once your balance clears whatever cash cushion your provider requires, usually $1,000 to $2,000, you can invest the rest in index funds inside the account, the same way you would in a 401(k). Now the third tax break does real work. The growth is tax-free, so a fund that doubles inside an HSA hands you the full gain with no capital gains tax waiting on the other side. You can model the difference in our compound interest calculator by running the same contribution with and without a tax drag on the growth.

Here is the part that feels like a cheat code. You do not have to spend the HSA on medical bills the year you have them. The IRS lets you reimburse yourself for a qualified expense any time later, as long as the expense happened after you opened the account. So you pay today's $300 dentist bill out of your regular checking, save the receipt, and let the $300 you would have spent stay invested in the HSA for 20 years. Two decades later you can pull that money out tax-free using the old receipt, after it has quadrupled. The account becomes a tax-free investment vehicle that you happen to be allowed to tap for free whenever a medical receipt justifies it.

The stealth retirement account

After you turn 65, the HSA changes shape. You can withdraw the money for any reason at all and just pay ordinary income tax on it, exactly like a traditional IRA. The 20% penalty that applies to non-medical withdrawals before 65 disappears. So in the worst case, where you somehow never had a single medical expense to claim, the HSA still behaves like a traditional retirement account. And in the realistic case, where you have decades of saved receipts plus the guaranteed flood of medical and dental costs that comes with age, most of it comes out tax-free anyway.

Stack that against the accounts you already know. A traditional 401(k) is taxed on the way out. A Roth IRA was taxed on the way in. The HSA can dodge tax on both ends if you use it for medical costs, which is why it ranks above both for the slice of your savings you can route into it. If you are weighing where each dollar should go, the taxes guide lays out the order, and the HSA usually sits right after grabbing your full employer match.

Worked example: $4,000 a year for 30 years

Say you are 28, you have an HDHP, and you can route $4,000 a year into the HSA and invest all of it. You pay your actual medical bills out of pocket and never touch the account, letting it grow at 7% a year, a reasonable long-run estimate for a stock-heavy fund.

You contributed $120,000 over 30 years and ended with about $378,000. The $258,000 of growth on top is the part that matters. In a regular brokerage account you would owe capital gains tax on that growth. In a traditional 401(k) you would owe ordinary income tax on the whole $378,000 when you withdraw it. In this HSA, every dollar of that $378,000 can come out tax-free, because over 30 years you will have racked up far more than $378,000 in medical, dental, vision, and prescription receipts, and you saved them. Run your own numbers and contribution amount through the compound interest calculator to see what your balance looks like.

Compare that to the same $4,000 a year sitting in a taxable account. Shave the return to roughly 6% after a yearly tax drag on dividends and rebalancing, and you land near $316,000, then still owe capital gains tax on the gains when you sell. The HSA's tax-free growth is worth tens of thousands of dollars on its own, before you even count the deduction you got going in.

What to actually do

• Check your plan. Confirm you have an HDHP. No HDHP, no HSA, full stop.
• Contribute through payroll if you can. That skips FICA on top of income tax, a break you cannot get any other way.
• Invest the balance. Move everything above the required cash cushion into a low-cost index fund inside the account.
• Pay medical bills from checking and save every receipt. Snap a photo, drop it in a folder, and let the HSA compound untouched.

Do that for a decade and you will have a six-figure pile of tax-free money that you can reach for the moment you decide you want it. Most people your age have never heard of this. That is the whole edge.

FAQ

Do I need a high-deductible health plan?

Yes, and it is the only hard requirement. For 2025 the plan must have a deductible of at least $1,650 for individual coverage or $3,300 for a family, and it has to meet the IRS out-of-pocket limits. You can only contribute for the months you are covered by a qualifying HDHP. If you switch to a low-deductible plan mid-year, you stop being eligible to add new money, though the balance you already built stays yours and keeps growing.

What if I do not use it for medical costs?

Before age 65, a non-medical withdrawal gets hit with ordinary income tax plus a 20% penalty, so do not raid it early for a vacation. After 65 the penalty vanishes. You can pull the money for anything and pay only ordinary income tax, exactly like a traditional IRA. So the worst realistic outcome is that your HSA performs as well as a traditional retirement account, and the likely outcome is far better, since decades of saved receipts let most of it come out tax-free.

Can I invest the balance?

Almost always, yes. Most HSA providers let you invest anything above a small required cash balance, often $1,000 to $2,000, into index funds and ETFs. Check the fund menu and the fees, because some bank-run HSAs charge more than they should. If your workplace HSA has a weak investment option, you can move the balance to a provider with better funds, the same way you would roll over an old 401(k).

How does the HSA compare to a Roth IRA or 401(k)?

For medical spending the HSA wins outright, because it is tax-free on both ends while a 401(k) is taxed on the way out and a Roth was taxed on the way in. The common order is to grab your full employer 401(k) match first, then fund the HSA, then return to the 401(k) or a Roth IRA. The Roth IRA breakdown and the traditional versus Roth 401(k) comparison walk through where each account fits.