A flexible spending account saves money only if you will spend the money anyway

A flexible spending account (FSA) lets you set aside pre-tax dollars for medical expenses you know are coming. The tax savings are real—you avoid federal income tax, Social Security tax, and Medicare tax on that money. But the account has a hard rule: money you don't spend by the end of the plan year is gone. That forfeiture trap makes an FSA worth it only if you can predict your medical costs accurately and you will actually incur them.

The math is straightforward. If you set aside $2,500 in an FSA and your combined federal, Social Security, and Medicare tax rate is 25 percent, you save $625 in taxes. But if you only spend $1,800 and forfeit the remaining $700, you have lost money overall. The tax savings have to outweigh the risk that you will leave money on the table.

Key Takeaways

  • An FSA saves you money only if you spend all the money you contribute, because unused funds are forfeited at the end of the plan year.
  • The tax savings range from roughly 20 to 37 percent depending on your income and state taxes, but only on money you actually use.
  • You should contribute only the amount you are confident you will spend on copays, deductibles, prescriptions, dental work, vision care, or other out-of-pocket medical costs.
  • If your medical needs are unpredictable or you rarely have out-of-pocket expenses, an FSA is riskier than a health savings account, which lets you carry money forward.

How the tax savings actually work

When you contribute to an FSA, that money comes out of your paycheck before taxes are calculated. If you earn $50,000 a year and contribute $2,500 to an FSA, your employer calculates taxes on $47,500 instead. The tax you avoid depends on your federal tax bracket, state income tax (if your state has it), Social Security tax at 6.2 percent, and Medicare tax at 1.45 percent.

For someone in the 22 percent federal bracket with state income tax and both payroll taxes, the combined rate is often 30 to 37 percent. For someone in the 12 percent federal bracket, it might be 20 to 25 percent. The higher your tax bracket, the more you save per dollar contributed. But that savings only applies to money you spend. If you contribute $2,500 and spend $1,800, you save taxes only on the $1,800.

When an FSA makes sense

An FSA is worth it if you have predictable, recurring medical expenses. Common scenarios include ongoing prescriptions you refill every month, annual dental work you schedule in advance, vision care you know you need, or a deductible you hit reliably every year. If you have a child in braces, a spouse with a chronic condition requiring regular copays, or you are planning elective surgery, you can estimate your costs with reasonable confidence.

The account also works well if your employer offers a grace period or a carryover option. Some plans let you carry forward up to $610 (the 2024 limit, which changes yearly) into the next plan year, or they give you a 2.5-month grace period after the year ends to spend remaining funds. Check your plan documents—if your employer offers either option, the forfeiture risk drops significantly.

When an FSA is a gamble

An FSA is risky if your medical needs are unpredictable. If you rarely see a doctor, have no prescriptions, and do not know whether you will need dental work this year, you cannot safely estimate how much to contribute. Contributing $2,500 and spending $800 means you forfeit $1,700, wiping out your tax savings and then some.

An FSA is also less attractive if you have a high-deductible health plan paired with a health savings account (HSA). An HSA has no forfeiture rule—money rolls over year to year and grows like a retirement account. If you can afford to contribute to both, the HSA is the safer choice because you keep the money either way. You can use an FSA for expenses the HSA does not cover, like dental and vision, but only if you are confident about those costs.

How much to contribute

The IRS sets an annual limit on FSA contributions. For 2024, the limit is $3,200 for individual coverage. Your employer may set a lower limit. You choose your contribution amount during open enrollment, and that amount is locked in for the plan year—you cannot change it unless you have a may have access to life event like a birth, marriage, or loss of coverage.

To decide how much to contribute, list your predictable medical expenses for the coming year: copays for regular doctor visits, prescription refills, dental cleanings and work, vision exams and glasses or contacts, and any planned procedures. Add them up. That total is the amount you should contribute, minus a small buffer if you are uncertain. If you cannot predict your costs within a few hundred dollars, contribute less or skip the FSA.

What expenses the FSA covers

An FSA covers most out-of-pocket medical costs: copays, coinsurance, deductibles, prescription drugs, dental care, vision care, hearing aids, and medical equipment like crutches or blood pressure monitors. It does not cover health insurance premiums, over-the-counter medications (unless prescribed by a doctor), cosmetic procedures, or gym memberships. Keep receipts and explanation of benefits statements—you may need to show proof that an expense was medical.

Some expenses are less obvious. Acupuncture, chiropractic care, and mental health counseling are covered if a doctor orders them. Prescription sunglasses are covered; non-prescription sunglasses are not. If you are unsure whether an expense qualifies, ask your FSA administrator before you spend the money.

The forfeiture rule and how to avoid it

Money left in your FSA at the end of the plan year is forfeited—you lose it. This is called the "use-it-or-lose-it" rule, and it is the biggest reason FSAs are risky. Some employers offer a grace period (usually 2.5 months into the next year) to spend remaining funds, or they let you carry over up to $610. If your plan offers either, you have more flexibility. If not, you need to spend the money by the deadline or lose it.

To avoid forfeiture, spend down your FSA balance before the plan year ends. Use it for dental work you have been putting off, stock up on prescription refills, buy glasses or contacts, or pay for any medical services you have been considering. Some people schedule elective procedures or dental cleanings in December specifically to use their FSA balance. It is not ideal, but it is better than forfeiting the money.

FSA versus HSA: which is better

If you have access to both an FSA and an HSA, the HSA is usually the better choice because money rolls over indefinitely and you keep it even if you change jobs. An HSA also earns interest or investment returns if you invest the balance. The downside is that an HSA requires a high-deductible health plan, which means higher out-of-pocket costs upfront.

You can use both accounts in the same year, but with a rule: you cannot use the FSA to pay for expenses that the HSA already covers. In practice, many people use the HSA for medical expenses and the FSA for dental and vision, since those costs are often predictable. If you have only an FSA option, it is still worth it if you can predict your spending. If you have an HSA option, prioritize that first.

Frequently Asked Questions

What happens to my FSA money if I leave my job?

You lose access to the account immediately, but you have a grace period (usually 60 to 90 days) to submit claims for expenses you incurred while employed. Any money you do not claim is forfeited. Some employers offer COBRA continuation, which lets you keep the FSA for a limited time, but you have to pay the full premium yourself.

Can I use my FSA debit card for anything, or only medical expenses?

The card is restricted to medical expenses. If you try to use it for groceries or gas, the transaction will be declined. Some cards require a receipt to prove the expense was medical. Keep all receipts and statements in case your FSA administrator asks for proof.

What if I contribute too much and cannot spend it all?

You forfeit the unspent balance at the end of the plan year, unless your plan offers a grace period or carryover. The only way to recover money is if you have a may have access to life event (like losing coverage) that lets you withdraw your balance. Otherwise, the money is gone. This is why contributing conservatively is safer than overestimating.

Can I use my FSA for my spouse or children?

Yes, if they are covered under your health plan. You can use FSA funds for their copays, prescriptions, dental work, and other medical expenses. You cannot use it for a spouse or child who is not on your plan.

Is an FSA worth it if my employer contributes to it?

Yes, absolutely. Some employers add money to employee FSAs as a benefit. If your employer contributes, that is assistance programs on top of your tax savings. Contribute enough to capture the full employer match, then decide whether to contribute more based on your predicted medical costs.