The core difference: what you can do with leftover money

An HSA (Health Savings Account) lets you keep unused money year after year. A Flexible Spending Account (FSA) requires you to spend what you set aside each year or lose it. That single rule shapes almost everything else about how these accounts work.

Both accounts let you set aside pre-tax dollars to pay for medical expenses your insurance doesn't cover. Both reduce your taxable income. But an HSA is designed as a long-term savings tool you can tap decades later, while an FSA is designed to help you pay for this year's out-of-pocket costs.

The choice matters because it changes how much you should contribute, what you can use the money for, and whether you'll actually get to use what you set aside.

Key Takeaways

  • HSA money rolls over year to year and grows tax-free, while FSA money follows a use-it-or-lose-it rule that resets each January.
  • You can only open an HSA if your health insurance is a high-deductible plan; FSA has no insurance requirement.
  • HSA contributions are lower ($4,150 individual / $8,300 family in 2024), but you can invest the balance and withdraw it tax-free in retirement for any expense.
  • FSA contributions are higher ($3,300 in 2024) but only cover medical, dental, and vision costs, and unused money disappears.
  • An HSA works best if you can afford to pay medical bills out of pocket and let the account grow; an FSA works best if you have predictable annual expenses you know you'll spend.

may be able to access: who can open each account

To open an HSA, you must be enrolled in a high-deductible health plan (HDHP). Your employer or insurance company will tell you whether your plan qualifies. In 2024, an HDHP has a deductible of at least $1,600 for individual coverage or $3,200 for family coverage. You cannot have other health coverage at the same time (with narrow exceptions for accident, disability, or dental-only plans).

An FSA has no insurance requirement. You can open one through your employer's benefits plan regardless of what health insurance you carry. Some employers offer both; some offer only one.

Both accounts are employer-sponsored. You cannot open either one on your own through a bank or insurance company. If your employer does not offer the account type you want, you cannot get it.

How much you can contribute each year

HSA contribution limits are set by the IRS and change annually. For 2024, you can contribute up to $4,150 if you have individual coverage or $8,300 if you have family coverage. These limits are higher than FSA limits because HSA money is yours to keep.

FSA contribution limits are also set by the IRS. For 2024, the limit is $3,300 per year. This is a hard cap across all FSAs you might have (though most people have only one through their employer).

Both contributions come directly from your paycheck before taxes, which lowers your taxable income for the year. If you contribute $3,300 to an FSA, you pay federal income tax, Social Security tax, and Medicare tax on $3,300 less of your salary.

What happens to money you don't spend

HSA money that you don't spend stays in your account. It rolls over to the next year, and the year after that, indefinitely. The balance grows tax-free if you invest it (most HSA providers let you invest in mutual funds or other securities). You can withdraw it at any time for any reason, though non-medical withdrawals before age 65 are taxed as income plus a 20% penalty. After 65, you can withdraw for any reason without penalty, though non-medical withdrawals are still taxed as income.

FSA money that you don't spend by the end of the plan year is forfeited. You lose it. Most plans have a "grace period" of 2.5 months into the next year (so through mid-March if your plan year ends December 31), but after that, any unspent balance is gone. Some employers offer a "carryover" option that lets you roll $640 into the next year, but this is optional and not all employers provide it.

What you can spend the money on

Both accounts cover the same categories of medical expenses: deductibles, copays, coinsurance, prescription drugs, dental work, vision care, hearing aids, and other costs that the IRS classifies as medical care. Both accounts can pay for items your insurance doesn't cover, like certain over-the-counter medications (with a prescription) or orthodontia.

The difference is what happens after you turn 65 or retire. HSA money can be withdrawn tax-free for Medicare premiums, long-term care insurance, and certain other health costs in retirement. FSA money cannot be used after you leave your job—the account closes when your employment ends or your employer's plan year ends.

How to use the money when you need it

Both accounts issue a debit card or reimbursement process. You can use the card at the pharmacy, doctor's office, or medical supplier, and the charge is deducted from your account balance. Or you can pay out of pocket and request reimbursement by submitting receipts to the account administrator.

The key difference is timing. With an FSA, you know you have a limited window to spend the money. Most people use FSA debit cards throughout the year and don't worry about tracking receipts until the end of the year. With an HSA, you can spend when ready or wait years—the money is always there, so there is no pressure to use it quickly.

Which account makes sense for your situation

Choose an HSA if you are enrolled in a high-deductible plan and can afford to pay medical bills out of pocket without touching the account. The real value of an HSA is that it grows tax-free over decades. If you withdraw the money for medical expenses, you pay no tax. If you leave it invested and withdraw it in retirement for non-medical expenses after 65, you pay income tax but no penalty. This makes an HSA a powerful retirement savings tool on top of its medical purpose.

Choose an FSA if you have predictable annual medical expenses—regular prescriptions, ongoing therapy, dental work, or vision care—that you know you will spend within the year. An FSA is simpler because you don't have to track the money long-term or worry about investment decisions. The higher contribution limit ($3,300 vs. $4,150) matters less because you are spending the money anyway.

If your employer offers both, you can open both in the same year. Some people use an FSA to cover predictable costs and an HSA to save for future medical or retirement expenses. Check your employer's plan documents to see whether this is allowed.

Frequently Asked Questions

Can I change my mind and switch from FSA to HSA mid-year?

No. Both accounts are tied to your employer's benefits plan year, which typically runs January through December. You can change your election during open enrollment (usually October or November) or if you have a may have access to life event like a job change, marriage, or birth. If you switch to an HDHP mid-year, you may be able to open an HSA, but you cannot retroactively contribute for the months before the switch.

What happens to my HSA if I leave my job?

Your HSA stays with you. It is your account, not your employer's. You can keep the balance, continue to invest it, and withdraw from it whenever you need to. You will need to move it to an HSA offered by a bank or financial institution if your new employer does not offer an HSA, but the money itself never disappears. An FSA, by contrast, closes when you leave your job.

Can I use HSA or FSA money to pay for health insurance premiums?

HSA money can pay for health insurance premiums only if you are receiving unemployment benefits or are retired and paying for Medicare, COBRA, or long-term care insurance. FSA money cannot pay for health insurance premiums at all. Both can pay for copays and deductibles under your current plan.

What if I contribute to an HSA but don't use the money for medical expenses?

You can leave it invested and use it later, even decades later. If you withdraw it for non-medical expenses before age 65, you owe income tax plus a 20% penalty on the withdrawal amount. After age 65, you can withdraw for any reason and owe only income tax, no penalty. This makes an HSA a flexible retirement savings tool if you can afford to pay medical bills out of pocket.

Do I have to use my FSA debit card, or can I pay out of pocket and get reimbursed?

You can do either. Some people use the debit card for convenience. Others pay out of pocket and submit receipts for reimbursement, which gives them a paper trail and more control over when they access the money. Both methods draw from the same account balance.