The core difference: how money moves and what happens to it

An HSA (Health Savings Account) and an FSA (Flexible Spending Account) both let you set aside pre-tax dollars for medical expenses, but they work in fundamentally different ways. The biggest difference is what happens to money you don't spend: HSA funds roll over to next year and stay yours forever, while FSA funds are typically forfeited if you don't use them by the end of the plan year.

An HSA is a savings account attached to a high-deductible health plan (HDHP). You own the account and the money in it, even after you leave your job or change insurance. An FSA is an account your employer sets up for you, and the money belongs to the plan — not to you personally. When the year ends, unspent FSA money usually goes back to your employer.

This single difference shapes almost everything else about how you use each account. It affects how much you can contribute, what you can buy with the money, and whether you should try to spend it all before December 31st.

Key Takeaways

  • HSA money rolls over year to year and stays yours even if you change jobs, while FSA money is forfeited at the end of the plan year unless your employer offers a carryover or grace period.
  • You can only open an HSA if you are enrolled in a high-deductible health plan, but an FSA is available through most employer health plans regardless of deductible.
  • HSA contribution limits are higher than FSA limits, and HSA funds can be invested to grow over time like a retirement account.
  • FSA has a "use it or lose it" rule that pushes you to spend the money within the plan year, while HSA encourages you to save for future medical costs.
  • Both accounts reduce your taxable income and let you pay for may be able to access medical expenses with pre-tax dollars.

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 may offer one, or you can buy one on your own through the health insurance marketplace. The IRS sets the minimum deductible each year — for 2024, it is $1,600 for individual coverage and $3,200 for family coverage. You cannot have other health coverage (with limited exceptions for accident, disability, or dental-only plans) and you cannot be claimed as a dependent on someone else's tax return.

An FSA has no such restrictions. If your employer offers one, you can open it regardless of what health plan you chose. You do not need a high-deductible plan, and you do not need to be enrolled in your employer's health insurance at all — some employers let employees on a spouse's plan or uninsured employees open an FSA.

This is why FSAs are more widely available: they work with any health plan. But it also means fewer people have the option to open an HSA, since not all employers offer high-deductible plans.

Contribution limits and who controls the money

HSA contribution limits are set by the IRS and are higher than FSA limits. For 2024, you can contribute up to $4,150 for individual coverage or $8,300 for family coverage to an HSA. Your employer may contribute on your behalf, and you can contribute the difference. If you are 55 or older, you can add an extra $1,000 per year.

FSA contribution limits are also set by the IRS but are lower. For 2024, the limit is $3,200 per year. Your employer sets the actual limit within that cap, and some employers go lower. Unlike an HSA, you cannot add extra contributions after age 55.

The money you contribute to an HSA is yours. You own the account, the balance, and any growth. If you leave your job, the account goes with you. If you stop using the HDHP, you keep the HSA and can still withdraw money for medical expenses tax-free — you just cannot make new contributions.

FSA money belongs to the plan, not to you. When you leave your job, you lose access to the account. If your employer closes the plan, the money is gone. This is why FSAs are sometimes called "use it or lose it" accounts.

The "use it or lose it" rule and carryover options

At the end of each FSA plan year, any money you did not spend is forfeited. This is the rule set by federal law. However, your employer can choose to offer two options that soften this rule: a carryover of up to $640 (for 2024) into the next year, or a grace period of up to 2.5 months after the plan year ends to spend remaining funds.

Not all employers offer these options, and not all offer both. Some offer carryover only, some offer a grace period only, and some offer neither. Check your plan documents or ask your benefits administrator which option your employer has chosen. If your employer offers both, you can use the grace period to spend money, and then carry over what is left.

An HSA has no "use it or lose it" rule. Money you do not spend stays in the account indefinitely. You can let it grow year after year, invest it like a retirement account, and withdraw it for medical expenses at any time in the future. This makes an HSA function more like a savings account than a spending account.

What you can buy with each account

Both HSA and FSA cover the same list of may be able to access medical expenses: doctor visits, prescriptions, dental work, vision care, mental health treatment, medical equipment, and many other healthcare costs. The IRS publishes a full list, and both accounts use the same rules about what qualifies.

The practical difference is in how you approach spending. With an FSA, you know you have until the end of the year (or the grace period) to spend the money, so you might stock up on glasses, hearing aids, or other durable medical items before the deadline. With an HSA, you can spread purchases across years and decades, so you might buy only what you need now and let the rest accumulate.

One major advantage of an HSA is that you can invest the balance. Once your account reaches a certain threshold (usually $1,000 to $2,500, depending on your provider), you can move money into mutual funds, stocks, or bonds. This lets your HSA grow like a retirement account. FSA funds typically sit in a cash account and earn little to no interest.

Tax treatment and how much you actually save

Both accounts reduce your taxable income. Money you contribute is deducted before income tax is calculated, so you pay no federal income tax, no Social Security tax, and no Medicare tax on the money you set aside. This is the same benefit whether you use an HSA or an FSA.

The tax savings depend on your tax bracket. If you are in the 22% federal tax bracket and contribute $3,200 to an FSA, you save about $704 in federal taxes alone. Add state income tax and payroll taxes, and the savings can reach 30% or more of what you contribute. An HSA gives you the same tax break on contributions.

Where an HSA pulls ahead is in the long term. Because HSA money rolls over and can be invested, you can accumulate years of tax-free growth. If you contribute $4,150 per year for 20 years and invest it, the account could grow to far more than the sum of your contributions. Withdrawals for medical expenses are tax-free, and you can withdraw at any age without penalty.

Which account makes sense for your situation

Choose an HSA if you are enrolled in a high-deductible health plan and expect to have medical expenses. The ability to roll over money year after year and invest it makes an HSA a powerful long-term savings tool. If you are healthy and do not spend much on medical care, an HSA lets you build a cushion for future expenses or retirement.

Choose an FSA if your employer does not offer an HSA, or if you are not enrolled in a high-deductible plan. An FSA is also useful if you have predictable, near-term medical expenses — like orthodontics, a planned surgery, or regular therapy — and you want to set aside money specifically for those costs this year. The lower contribution limit is less of a drawback if you know exactly how much you will spend.

If your employer offers both, you can open an HSA and an FSA at the same time, but there are limits on how much you can claim. Talk to your benefits administrator about the rules for your plan.

Frequently Asked Questions

What happens to my FSA money if I leave my job mid-year?

You lose access to the account immediately. Any money you have not spent is forfeited, even if you have not reached the end of the plan year. Some employers offer a continuation period (called COBRA for health insurance), but this does not extend FSA access. An HSA goes with you when you leave, so you keep the balance and can continue to use it.

Can I use my HSA to pay for my spouse's medical expenses?

Yes. HSA funds can be used for the medical expenses of you, your spouse, and any dependent children, regardless of whether they are covered under your health plan. The same rule applies to FSA funds.

What happens if I withdraw HSA money for something that is not a medical expense?

You owe income tax on the withdrawal, plus a 20% penalty if you are under 65. After age 65, you can withdraw money for any reason without the penalty, but you still owe income tax on non-medical withdrawals. FSA withdrawals for non-medical expenses are not allowed — you cannot withdraw the money at all.

Should I try to spend all my FSA money before the year ends?

Only if your employer does not offer a carryover or grace period. If they do, you can let some money roll over or use the grace period to decide later. If they do not, spending down the account before December 31st is the only way to avoid losing the money. Check your plan documents to see what your employer offers.

Can I have both an HSA and an FSA at the same time?

You can have an HSA and a limited-purpose FSA (which covers only dental and vision expenses) at the same time. You cannot have an HSA and a general-purpose FSA together in the same year. If you have both, the IRS treats it as a violation and you may owe taxes and penalties.