Most people open an HSA to cover this year's deductible and stop there. Using one as a long-term vehicle for future medical costs is a different strategy, and the rules that govern it are easy to misread. Here is the setup, the steps, and the places where the plan tends to break down.
What Health Savings Accounts for Future Medical Costs Actually Require Before You Start
The CFPB describes a health savings account as a tax-advantaged savings account available only to consumers enrolled in a High Deductible Health Plan (HDHP).1 That's the hard eligibility gate. If the plan covering you isn't an IRS-qualified HDHP, you can't contribute to an HSA at all - not partially - not temporarily. Check the plan documents first, before any other step.
The IRS sets contribution limits each year, and those limits change. Consult IRS Publication 969, Health Savings Accounts and Other Tax-Favored Health Plans, for the current figures before you contribute.2 Contributing over the limit triggers a 6 percent excise tax on the excess - assessed each year the excess remains in the account.
The background reason this strategy is worth the setup is plain in the numbers. According to KFF, out-of-pocket health spending had reached about $1,514 per person by 2023, compared to roughly $115 in 19703. And KFF also reports that total U.S. health spending grew about 7.5 percent from 2022 to 2023, faster than the 4.6 percent growth from 2021 to 2022.3 Medical costs compound. A savings vehicle that compounds with them - tax-free - has real arithmetic value over decades.
Open and Fund the Account: The First Concrete Step
Once HDHP enrollment is confirmed - open an HSA with a custodian - typically a bank, credit union, or brokerage. The account is yours individually, not tied to an employer, even if the employer offers payroll-deduction contributions. Choosing a custodian that allows investment of HSA balances matters for a long-term strategy - because cash sitting idle in an HSA doesn't keep pace with health cost inflation.
Fund the account up to the annual IRS limit. Contributions made by payroll deduction avoid both income tax and FICA taxes. Contributions made directly to the account avoid income tax only - they're deductible on the federal return - but don't escape FICA. For a W-2 employee, the payroll route is the more efficient of the two.
Here is a worked example of how the tax benefit stacks up over time. Suppose an individual contributes about $4,000 per year to an HSA for 20 years, invests the balance in a diversified index fund, and earns an average annual return of 6 percent. After 20 years - the account holds roughly $147,000 in nominal terms. Every dollar of qualified medical expense withdrawn is tax-free - no income tax on the way in, no capital gains on growth, no tax on the way out for qualified costs. A comparable taxable brokerage account earning the same return and subject to a combined 25 percent marginal rate on gains would leave meaningfully less after taxes. That gap is the point of the strategy.
Build the Account Over Time and Let It Compound
The CFPB reports that about 36 million HSAs were open in 2023, collectively holding over $116 billion in assets - and that HSA assets have increased by more than 500 percent since 20131. The accounts growing fastest are almost certainly those invested, not just parked in cash. The custodian's investment menu matters here as much as the contribution level.
The key behavioral discipline for a future-cost strategy is this: pay current medical expenses out of pocket when you can afford to, and leave the HSA balance invested. There's no deadline on reimbursing yourself for a qualified medical expense. If you pay a $300 doctor bill today from your checking account, save the receipt. Five years from now - or twenty - you can still reimburse yourself from the HSA, tax-free and penalty-free - as long as the expense occurred after the account was open. This is the mechanic that allows the HSA to function like a long-horizon investment account rather than a medical checking account.
A plain side-by-side comparison shows the difference in approach. Strategy A: contribute $3,000 annually, spend it down each year on current medical costs, account balance stays near zero. Strategy B: contribute $3,000 annually - pay current costs from other funds, keep the HSA invested. After 15 years at 6 percent, Strategy A has produced roughly $3,000 in annual tax-free reimbursements and nothing more. Strategy B has produced a balance of roughly $74,000 - available for future costs - or, after age 65, for any expense at all .
Keep records. Every receipt, every Explanation of Benefits document, every invoice for a qualified expense paid out of pocket is a future tax-free withdrawal waiting to happen. The IRS doesn't specify a particular record format - but it does require substantiation for all distributions claimed as qualified.2
Where the Plan Tends to Break Down
The most common point of failure is loss of HDHP coverage. The moment a person switches to a non-HDHP plan - through a job change, a life event, or Medicare enrollment at age 65 - HSA contributions must stop. Existing balances remain intact and can still be spent on qualified expenses tax-free, but no new money goes in. Many people don't plan for this transition and contribute in a year when they were only partially covered by an HDHP, which creates a pro-rated limit calculation and potential excess contribution penalties.
Medicare enrollment is the most predictable disruption. Once enrolled in any part of Medicare - HSA contributions cease entirely. Planning the contribution schedule around an anticipated retirement and Medicare start date is worth doing explicitly, not leaving to chance.
A second sticking point is the definition of qualified medical expenses. According to the IRS, qualified expenses include payments for legal medical services rendered by physicians, surgeons, dentists - and other medical practitioners.2 Expenses that are merely beneficial to general health - vitamins, cosmetic surgery without a medical indication - don't qualify.2 A distribution taken for a non-qualified expense before age 65 is subject to both ordinary income tax and a 20 percent penalty. After age 65 the penalty disappears, but income tax still applies. Spending the account on a non-qualified item is a material cost.
Also note: the standard Schedule A medical expense deduction and an HSA reimbursement can't both apply to the same expense. According to the IRS, only the portion of medical and dental expenses exceeding 7.5 percent of adjusted gross income is deductible on Schedule A.2 If an expense is reimbursed from an HSA, it can't also be deducted. Double-dipping isn't permitted - and the IRS checks for it.
Myths Worth Clearing Up
Myth one: the money must be used by year-end or it's forfeited. That's a Flexible Spending Account rule, not an HSA rule. HSA balances roll over indefinitely. There's no use-it-or-lose-it clock. This confusion leads some people to spend down their HSA in December when they should be leaving the balance invested.
Myth two: an HSA is only useful for people with high current medical costs. The opposite is closer to the truth for a long-term strategy. Someone who is relatively healthy, can afford to pay current costs out of pocket, and has HDHP coverage is the ideal candidate - because they can contribute the maximum, invest it - and leave it untouched for decades. The CFPB notes that HSAs were established specifically to provide tax benefits to individuals with HDHPs,1 but the long-run compounding benefit accrues most to those who treat the account as an investment vehicle rather than a spending account.
Myth three: HSA funds can't be invested in the market. Most custodians offer investment options once the account balance clears a minimum threshold (often around $1,000, though this varies by custodian). Leaving the entire balance in cash is a choice, not a requirement - and for a 20-year horizon - it's generally the wrong choice given how fast health costs grow. KFF reports that health care now represents about 18 percent of U.S. GDP.3
Myth four: the HSA becomes worthless after age 65. After 65, non-medical withdrawals are taxed as ordinary income, the same as a traditional IRA - but no penalty applies. Qualified medical withdrawals remain completely tax-free. At an age when health costs typically rise sharply, a large invested HSA balance is arguably more valuable, not less. The account doesn't expire.
This strategy is well-suited to people who have access to an HDHP - can absorb current medical costs from other funds, and have a long enough horizon to let the balance grow. It's less suitable for people who need the HSA as an immediate medical cash reserve, who have high ongoing medical expenses that require drawing down the account each year, or who are close to Medicare enrollment and have limited time to build the balance. For questions about your own tax situation, consult a qualified tax professional - the IRS rules in this area have real edges and the penalties for errors aren't small.
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Disclaimer
This article is for general informational purposes only and isn't financial - investment, insurance, or tax advice. Rates, fees, and rules change and vary by lender and situation. For decisions about your own money - consult a qualified financial professional.
