A flex spending account lets you set aside pretax money from your paycheck to pay for medical expenses your insurance doesn't cover

A flexible spending account (FSA) is an employer-sponsored plan where you contribute money before taxes are taken out, then use that money to pay for may be able to access medical costs. Your employer deducts your contribution from your paycheck throughout the year, which lowers your taxable income. You decide how much to contribute each year during open enrollment, and that money sits in an account you control. When you have a medical expense — copays, deductibles, prescriptions, dental work, vision care — you submit a claim or use a debit card to pay for it from your FSA balance.

The main trade-off is the use-it-or-lose-it rule: money you don't spend by the end of the plan year (usually December 31) goes back to your employer. You cannot carry it forward to the next year, and you cannot get it back as a refund. This is why choosing the right contribution amount matters — you need to estimate what you'll actually spend, not what you might spend.

Key Takeaways

  • You contribute pretax money through payroll deductions, which reduces the income taxes and Social Security taxes you owe that year.
  • You can use FSA money only for may be able to access medical expenses: copays, deductibles, prescriptions, dental, vision, and certain medical equipment and supplies.
  • Money left in your account at the end of the plan year is forfeited — there is no carryover and no refund, so estimate conservatively.
  • Most FSAs let you claim reimbursement by submitting receipts or using a debit card tied to the account, and you can request money back anytime during the year.
  • You can change your contribution amount only during open enrollment or if you have a may have access to life event like a birth, marriage, or loss of other coverage.

How money goes in: payroll deductions and tax savings

When you enroll in an FSA, you tell your employer how much you want to contribute for the year. That amount is divided by the number of pay periods, and your employer deducts that portion from each paycheck before calculating income tax and Social Security tax. If you contribute $2,400 for the year and get paid twice a month, your employer deducts $100 from each paycheck.

The tax savings come from the fact that this money is not counted as income. If you're in the 22% federal tax bracket and contribute $2,400, you save roughly $528 in federal income tax alone, plus Social Security and Medicare taxes. Your take-home pay is lower by the full contribution amount, but your actual out-of-pocket cost is lower because you're not paying taxes on that money.

Your employer may also contribute to your FSA — some employers add a small amount to help employees participate. Check your plan documents or ask your benefits administrator whether your employer makes contributions.

What expenses you can and cannot pay for

FSA money covers most medical, dental, and vision expenses that your insurance does not pay for. This includes copays, coinsurance, deductibles, prescription medications, dental cleanings and fillings, eyeglasses and contact lenses, hearing aids, and certain over-the-counter items like pain relievers and allergy medicine (though over-the-counter drugs now require a prescription to may have access to). You can also use FSA money for medical equipment like crutches, blood pressure monitors, or glucose meters.

FSA money does not cover health insurance premiums, cosmetic procedures, gym memberships, vitamins (unless prescribed by a doctor), or general wellness products. If you're unsure whether a specific expense qualifies, ask your FSA plan administrator or check the IRS Publication 502, which lists all may be able to access medical expenses.

One important detail: you can use FSA money only for expenses incurred during the plan year. If you have dental work done in December but don't pay the bill until January, you cannot use FSA funds from the previous year to pay it. The date the service was provided matters, not the date you pay.

How to get money out: reimbursement and debit cards

There are two main ways to access your FSA balance. Many plans issue a debit card linked to your account. You use it like a regular debit card at pharmacies, doctor's offices, and other medical providers. The card automatically deducts from your FSA balance. This is the fastest method because you don't have to submit paperwork.

The other method is reimbursement by claim. You pay for the medical expense out of pocket, then submit a claim to your FSA administrator with a receipt or explanation of benefits. The administrator reviews the claim, confirms the expense is may be able to access, and deposits the reimbursement into your bank account. This usually takes one to two weeks. Some plans require you to use this method for certain types of expenses, or they may require it if you don't have a debit card.

You can request reimbursement anytime during the year, even if you haven't finished spending your full contribution. There's no limit on how many claims you can submit. Keep all receipts and documentation for at least three years in case your plan administrator asks for proof.

The use-it-or-lose-it rule and how to plan around it

This is the biggest risk with an FSA: any money left in your account on December 31 (or the last day of your plan year) is forfeited. Your employer keeps it. You cannot roll it over to next year, and you cannot withdraw it as cash. This rule exists because of IRS regulations, and almost all employer FSAs follow it.

To avoid losing money, estimate your medical spending conservatively. Look at what you actually spent on copays, prescriptions, and other may be able to access expenses over the past year or two. If you're unsure, start with a lower amount — you can always increase it next year. Common contribution amounts range from $500 to $2,750 per year, depending on your expected spending and your employer's plan limits.

If you have a major medical event coming up — surgery, orthodontics, or a planned procedure — that's a good year to contribute more. If you're healthy and rarely visit the doctor, contribute less. The key is matching your contribution to what you'll realistically spend.

When you can change your contribution or stop participating

You can change your FSA contribution only during your employer's open enrollment period, which is usually once a year in the fall. Changes take effect January 1 of the following year. If you don't change anything, your contribution amount stays the same.

You can also change your contribution if you have a may have access to life event: birth or adoption of a child, marriage or divorce, loss of spouse's health coverage, significant change in medical expenses, or change in your employment status. You typically have 30 to 60 days after the event to notify your benefits administrator and make changes. Different employers have different rules, so check your plan documents.

If you leave your job, your FSA coverage usually ends on your last day of employment. You can use any remaining balance through the end of the plan year (usually December 31), but you cannot access it after that. If you're changing jobs, ask your new employer whether they offer an FSA so you can continue participating.

FSA vs. health savings account: which is right for you

An FSA and a health savings account (HSA) are both pretax accounts for medical expenses, but they work differently. An FSA has the use-it-or-lose-it rule and is available through most employers. An HSA requires a high-deductible health plan, has no use-it-or-lose-it rule, and lets you carry money forward indefinitely. HSAs also let you invest the balance, which FSAs do not.

If your employer offers both, an HSA is usually the better choice because you keep the money and can invest it for retirement. But not everyone qualifies for an HSA — you need to be enrolled in a high-deductible plan. If your employer offers only an FSA, or if you're on a traditional health plan, an FSA can still save you money on taxes and help you budget for predictable medical costs.

Some employers let you have both an FSA and an HSA, but there are limits on how much you can contribute to each. Talk to your benefits administrator about what combination makes sense for your situation.

Frequently Asked Questions

What happens to my FSA money if I don't use it by the end of the year?

The money is forfeited and returned to your employer. You cannot carry it forward, get a refund, or access it after the plan year ends. This is why estimating your spending carefully is important — contribute only what you're confident you'll spend.

Can I use my FSA debit card at any store?

No. FSA debit cards work only at pharmacies, doctor's offices, dental offices, vision care providers, and other medical merchants. They will not work at grocery stores or general retailers, even if those stores sell over-the-counter medical items. Some online pharmacies and medical suppliers also accept FSA cards.

Do I need receipts to use my FSA?

If you use a debit card, you may not need to submit a receipt immediately, but your plan administrator can ask for proof later. If you're claiming reimbursement, you must submit a receipt or explanation of benefits showing the expense was incurred. Keep all documentation for at least three years.

Can I withdraw money from my FSA if I don't have a medical expense?

No. FSA money can be used only for may be able to access medical expenses. You cannot withdraw it as cash or use it for non-medical purposes. If you contribute money and don't spend it on medical care, you lose it at the end of the year.

What if I change jobs mid-year?

Your FSA coverage usually ends on your last day of employment. You can use any remaining balance through the end of the plan year if your employer allows it, but you cannot access the money after that. If your new employer offers an FSA, you can enroll during their open enrollment or if you have a may have access to event.