Open enrollment season is here, and millions of Americans are staring at a benefits form that asks one deceptively simple question: do you want an FSA or an HSA?
Picking wrong can cost you hundreds of dollars you never get back.
The two accounts sound almost identical, but the rules around who owns the money, when you can spend it, and what happens if you switch jobs are completely different.
Start with the health savings account, or HSA.
It is only available if you are enrolled in a high-deductible health plan, which in 2025 means a deductible of at least $1,650 for an individual or $3,300 for a family.
The payoff is real: contributions are tax-free going in, grow tax-free, and come out tax-free for qualified medical costs.
Your unused balance rolls over every year, and the account is yours forever, even if you change employers.
The flexible spending account, or FSA, works differently.
It is offered through your job and is not tied to a high-deductible plan, so it is often the only option for people in traditional coverage.
You decide how much to set aside, and that money comes out of your paycheck before taxes.
Many employers give you until March 15 of the following year to spend last year's funds, and some allow a carryover of $660 in 2025, but plenty of workers forfeit money every single year.
Here is the part that surprises people most: an FSA is funded upfront.
If you elect $2,000 for the year, your employer makes the full amount available on day one, even though you have only contributed a few hundred dollars so far.
An HSA only lets you spend what you have actually deposited.
That upfront access can matter if a big medical bill lands in January.
Both accounts let you skip federal income tax and, in most cases, payroll taxes on the money you contribute.
The 2025 limits are $4,300 for an HSA individual and $8,550 for a family, plus a $1,000 catch-up if you are 55 or older.
FSA limits are $3,300 per employee, with a $660 carryover option.
If your employer offers both, which is rare but possible with a limited-purpose FSA, you can pair them.
The decision usually comes down to two questions.
Do you expect steady medical costs you can predict, like glasses, dental work, or regular prescriptions?
An FSA can work if you are confident about the number.
Do you want an account that grows, follows you between jobs, and can be invested for retirement?
An HSA wins, and many financial planners treat it as a stealth retirement account.
One warning: switching health plans mid-year can disqualify you from contributing to an HSA, and any money already in the account stays yours but stops growing tax-free.
Read the fine print before you change coverage.
Also check whether your employer kicks in matching dollars, which is free money either way.
Our take: if you qualify for an HSA, fund it as generously as your budget allows and invest the balance once it clears a comfortable cash cushion.
If an FSA is your only option, estimate low rather than high, because unspent dollars vanish.
Final Thoughts
A quick calculation now beats discovering next spring that you donated your own money to your employer's bottom line.