FSAs save money only if you will actually spend the money you set aside
A Flexible Spending Account (FSA) reduces your taxable income by letting you set aside pre-tax dollars for medical expenses. The math works like this: if you earn $50,000 and contribute $3,000 to an FSA, you pay income tax on $47,000 instead. At a 22% federal tax rate, that saves you roughly $660 in taxes that year.
But that tax savings only matters if you spend the money. FSAs have a critical rule: money you don't use by the end of the plan year is forfeited. You cannot roll it over to next year, and you cannot get it back. This rule—called the "use-it-or-lose-it" provision—is what makes FSAs risky for many people. If you set aside $2,500 and only spend $1,800, you lose $700 entirely. The tax savings disappear, and you've actually lost money.
Whether an FSA is worth it depends on three things: how much you spend on may be able to access medical expenses in a typical year, how confident you are about that number, and whether you can afford to lose the money if you guess wrong.
Key Takeaways
- FSAs only save money if you spend all the money you contribute; unspent funds are forfeited at year-end with no exceptions.
- The tax savings from an FSA contribution ranges from roughly 20% to 40% of the amount you set aside, depending on your income tax bracket.
- FSAs work best for people with predictable medical expenses—regular prescriptions, ongoing therapy, dental work, or vision care scheduled in advance.
- If your medical spending varies wildly year to year, or if you cannot afford to lose money you don't spend, an HSA (if available) is usually safer.
- Most employers allow you to change your FSA contribution once per year during open enrollment, but mid-year changes require a may have access to life event.
How much you typically spend on may be able to access medical expenses
Start by looking at what you actually paid out of pocket for medical care in the past two years. Pull up your insurance statements, pharmacy receipts, and credit card records. Count only expenses that FSAs cover: copays, coinsurance, deductibles, prescription drugs, dental work, vision care, mental health visits, and over-the-counter items like pain relievers and allergy medicine (with a prescription).
Do not count health insurance premiums, cosmetic procedures, or gym memberships. If you have a spouse or dependents, include their may be able to access expenses too—you can use FSA funds for anyone on your tax return, not just yourself.
Once you have a number, ask yourself: is this amount roughly the same every year, or does it swing wildly? If you spent $2,200 last year and $2,100 the year before, you have predictable spending. If you spent $800 one year and $4,500 the next, your spending is unpredictable, and an FSA becomes a gamble.
The tax savings calculation and when it actually helps
The amount you save in taxes depends on your tax bracket. If you contribute $2,500 to an FSA, the tax savings range from roughly $500 (at a 20% combined federal and state rate) to $1,000 (at a 40% rate for high earners). That is real money, but only if you spend the full $2,500.
Here is where the math breaks down: if you contribute $2,500 and spend only $2,000, you save taxes on $2,000 (roughly $400 to $800), but you lose $500 in unspent funds. Your net gain is smaller than you expected. If you spend only $1,500, you might break even or lose money entirely.
The FSA is worth it when your expected spending is high enough and certain enough that you are confident you will spend most or all of what you contribute. For someone with a chronic condition requiring regular medication, ongoing therapy, or scheduled dental work, that confidence is easier to have. For someone with no regular medical expenses and occasional doctor visits, it is much harder.
FSA versus HSA: which is the better choice
If your employer offers both an FSA and a Health Savings Account (HSA), the HSA is almost always the safer choice. HSAs do not have a use-it-or-lose-it rule. Money you don't spend rolls over to the next year, and the next, indefinitely. You can invest the balance and let it grow. This removes the guessing game entirely.
The trade-off is that HSAs require you to be enrolled in a high-deductible health plan (HDHP), which means higher out-of-pocket costs when you do use medical care. An FSA works with any health plan. If your employer offers an HSA and you are enrolled in an HDHP, choose the HSA. If your employer offers only an FSA, or if you are not may be able to access for an HSA, then the FSA decision comes down to how predictable your spending is.
Some people use both: they contribute a smaller amount to an FSA (for expenses they are certain about) and a larger amount to an HSA (for everything else). This strategy works only if your employer and health plan allow it.
The risk of guessing wrong and losing money
The use-it-or-lose-it rule has no exceptions. If you contribute $3,000 and spend $2,800, the remaining $200 vanishes. There is no carryover, no refund, no way to get it back. Some employers offer a "grace period" of up to 2.5 months into the next calendar year to spend remaining funds, but this is optional and not all employers provide it. Even with a grace period, you cannot carry money forward to the following year.
This rule exists because FSAs are a tax benefit, and the IRS treats unspent funds as a forfeiture. The money was never taxed, so you cannot get it back without triggering tax consequences.
The safest approach is to contribute only what you are very confident you will spend. If you are unsure, contribute less. A smaller contribution with full spending is better than a larger contribution with leftover funds. You can always increase your contribution next year during open enrollment if you realize you spent more than you expected.
When an FSA makes the most sense
An FSA is worth it for people in these situations: you take regular prescription medications; you have scheduled dental or vision work coming up; you receive ongoing mental health or physical therapy; you have a dependent with regular medical needs; or you have a high deductible and expect to meet it most years.
For these people, the spending is predictable enough that they can contribute with confidence. The tax savings are real, and the risk of forfeiture is low.
An FSA is not worth it if your medical spending is unpredictable, if you rarely visit a doctor, or if you cannot afford to lose money you don't spend. In these cases, the risk of forfeiture outweighs the tax savings. If an HSA is available to you, it is the better choice.
How to decide: a straightforward framework
Ask yourself these questions in order:
- Do I have access to an HSA through a high-deductible health plan? If yes, choose the HSA and stop here.
- How much did I spend on may be able to access medical expenses in the past two years? Calculate the average.
- Is that number roughly the same each year, or does it vary by more than 30%? If it varies widely, an FSA is risky.
- Can I afford to lose the money if I guess wrong? If no, do not contribute to an FSA.
- If I contribute, what amount am I very confident I will spend? Contribute that amount, not more.
The FSA is a tax-savings tool, not a savings account. It works best for people who know what they will spend and can afford the risk if they guess wrong.
Frequently Asked Questions
Can I change my FSA contribution mid-year?
Only if you have a may have access to life event: marriage, divorce, birth or adoption of a child, loss of health coverage, or a significant change in medical needs. Job changes and salary increases do not may have access to. Most people can change their contribution only during open enrollment, which is usually once per year in the fall.
What counts as an may be able to access FSA expense?
Copays, coinsurance, deductibles, prescription drugs, dental work, vision care, mental health visits, and over-the-counter medications (with a prescription) all count. Health insurance premiums, cosmetic procedures, and gym memberships do not. Your employer's FSA plan document lists all may be able to access expenses.
What happens to my FSA money if I leave my job?
You lose any unspent balance. FSA funds belong to your employer's plan, not to you. When you leave, you can continue coverage under COBRA for a limited time, but you cannot take the FSA balance with you. This is another reason to contribute conservatively.
Is there any way to get my unspent FSA money back?
No. The use-it-or-lose-it rule has no exceptions. Some employers offer a grace period of up to 2.5 months into the next year to spend remaining funds, but unspent money after that period is forfeited permanently. This is a tax rule, not an employer choice.
Should I contribute the maximum to my FSA?
Only if you are very confident you will spend it all. The maximum contribution for 2024 is $3,200 (this amount changes yearly). Contributing the maximum makes sense only if your medical spending reliably exceeds that amount. Otherwise, contribute only what you are sure you will spend.