Open enrollment season is here, and millions of Americans are about to make a choice that shapes their taxes and their health care bills for the entire year.
Two accounts sound nearly identical at the HR portal: the FSA and the HSA.
The flexible spending account, or FSA, lets you stash pre-tax dollars for medical costs.
The catch is brutal: in most cases, you must spend the money by December 31 or lose it.
Employers can offer a grace period or a small carryover, but many don't.
Last year, workers forfeited an estimated hundreds of millions of dollars in unused FSA funds, according to benefits industry tracking.
That's money deducted from paychecks that simply evaporated.
The health savings account, or HSA, works like a personal bank account for medical expenses, and the money rolls over year after year with no deadline.
To qualify, you must be enrolled in a high-deductible health plan.
For 2025, that means a deductible of at least $1,650 for individual coverage.
You can contribute up to $4,300 for yourself or $8,550 for family coverage, plus an extra $1,000 if you're 55 or older.
HSA contributions are tax-deductible, growth is tax-free, and withdrawals for qualified medical costs are tax-free too.
It's the only account in the tax code with that triple advantage.
Unlike an FSA, the HSA balance is yours forever.
If you switch jobs or retire, the account follows you.
Some workers invest the balance and let it grow for decades, treating it like a stealth retirement account.
The FSA still makes sense for one group: people who know exactly what they'll spend.
If you're managing a chronic condition, paying for regular therapy, or planning vision and dental work, an FSA can cover predictable costs, and it's available even if your employer's health plan isn't high-deductible.
Many employers also offer a dependent care FSA for childcare or elder care, which has no HSA equivalent.
Overestimating means you've locked up money you could have used elsewhere.
HSAs don't punish either mistake, which is why financial planners increasingly call them the better default for anyone who qualifies.
One more wrinkle worth knowing: you can't contribute to an HSA if you're enrolled in Medicare or claimed as a dependent on someone else's tax return.
And once you sign up for Social Security benefits, HSA contributions must stop.
If you're nearing retirement, that window closes faster than most people expect.
For 2025, the average American household spends roughly $1,300 out of pocket on health care beyond premiums, according to federal data.
Choosing the wrong account won't show up as a line item on your budget, but it quietly drains dollars that could have compounded instead.
Before you click submit on your benefits page, run the numbers on your actual spending from the past two years.
If your medical costs are steady and predictable, an FSA can work.
If they're lumpy, uncertain, or likely to grow, the HSA is usually the smarter move.
The real problem isn't that workers pick the wrong account.
It's that employers rarely explain the difference in plain language, and the default option often favors the company's bottom line over yours.
Final Thoughts
Read the fine print, ask HR directly about carryover rules, and don't let a December deadline decide what happens to your money.