Set aside enough to cover predictable medical costs you'll actually use before the year ends

The core decision is simple: put in only what you'll spend on may be able to access medical expenses between now and the end of the plan year. FSA money doesn't roll over to the next year — what you don't use, you lose. That's the trade-off. You get a tax break on the money you contribute, but you have to spend it or forfeit it.

Most people should start by listing the medical costs they know are coming: prescriptions they refill monthly, contact lens solution, copays for regular appointments, dental work already scheduled. Add those up for the full year. That number is your baseline. Then decide whether to go higher based on how much you typically spend on over-the-counter items like pain relievers, allergy medicine, or first aid supplies.

Key Takeaways

  • FSA contributions are deducted from your paycheck before taxes, so putting in $2,500 might actually cost you $1,800 to $1,900 depending on your tax bracket.
  • Money left in your FSA at the end of the plan year is forfeited — there is no rollover, so you need to estimate what you'll actually spend.
  • may be able to access expenses include prescription medications, copays, dental work, vision care, and many over-the-counter items like bandages and pain relievers.
  • If you're unsure about your spending, start with a conservative amount and increase it in future years once you see your actual patterns.

Calculate what you'll actually spend, not what you might

The biggest mistake is overestimating. People think about worst-case scenarios — a root canal, emergency glasses, an unexpected illness — and fund their FSA as if those things are certain to happen. They're not. You need to estimate based on what you reasonably expect to spend, not what could theoretically happen.

Pull up your receipts or insurance statements from the past year. Look at what you actually paid out of pocket for medical, dental, and vision care. Include prescription copays, over-the-counter medications you bought regularly, and any procedures you know are coming this year. If you had a one-time expense last year that won't repeat, don't count it.

Be honest about habits too. If you never buy over-the-counter allergy medicine, don't assume you'll start this year just because it's available through your FSA. If you see the dentist twice a year, count two cleanings and whatever work typically follows.

The tax savings make a lower contribution still worthwhile

Even if you're uncertain about your spending, putting something into an FSA usually makes financial sense because of the tax break. When you contribute $2,500 to an FSA, you don't pay federal income tax, Social Security tax, or Medicare tax on that money. Depending on your tax bracket, that $2,500 might only cost you $1,800 to $1,900 in actual take-home pay.

That means if you contribute conservatively — say $1,500 instead of $2,500 because you're worried about losing money — you're still coming out ahead compared to paying for those same expenses with after-tax dollars. The tax savings cushion some of the risk of forfeiting unused money.

The math changes if you're in a very low tax bracket or if you rarely spend on medical care. But for most people with regular prescriptions, copays, or dental work, even a modest FSA contribution saves money overall.

Account for changes in your health or coverage during the year

Your medical spending isn't always predictable. A new prescription, a planned surgery, or a change in your insurance plan can shift what you'll actually spend. If you know a major expense is coming — braces for your child, a scheduled procedure, new glasses — factor that in. If you're starting a new medication, ask your doctor or pharmacist how much it will cost over the year.

Some changes happen after you've already chosen your FSA amount. If you switch to a plan with higher copays mid-year, you might spend more than you anticipated. If you lose a dependent or change insurance, your costs might drop. The FSA rules do allow you to change your contribution amount if you have a may have access to life event — a birth, adoption, marriage, divorce, or loss of coverage — but not for routine changes in spending patterns.

Start conservative if this is your first FSA

If you've never had an FSA before, you don't have your own spending history to work from. In that case, start with a number you're confident you'll spend: your regular prescription copays plus a modest buffer for over-the-counter items. You can always increase your contribution next year once you see what you actually used.

Many employers allow you to change your FSA election during open enrollment each year, so this year's choice doesn't lock you in forever. If you contribute $1,500 and realize by October that you'll easily spend $2,500, you're stuck with the lower amount for this year. But you can adjust upward for next year. The risk of going too low is smaller than the risk of losing money by going too high.

Track your spending throughout the year

Once you've chosen an amount, don't set it and forget it. Keep receipts and monitor how much you've spent as the year goes on. Most FSA providers let you check your balance online or through an app. By mid-year, you should have a sense of whether you're on track to spend what you contributed.

If you're spending faster than expected, you might need to adjust your habits or plan for additional expenses. If you're spending slower, you have time to use up the balance before the year ends. Some plans offer a grace period of up to 2.5 months into the next year to spend down your balance, but not all do — check your plan documents to know for sure.

Frequently Asked Questions

What happens to money I don't spend in my FSA?

You forfeit it. FSA money does not roll over to the next year. Some plans offer a grace period of up to 2.5 months into the following year to spend remaining funds, but after that, any unused balance is gone. This is why estimating conservatively matters.

Can I change my FSA contribution amount during the year?

Only if you have a may have access to life event: birth, adoption, marriage, divorce, loss of coverage, or a significant change in your spouse's benefits. Routine changes in spending or concerns about forfeiting money don't may have access to. You can change your amount during the next open enrollment period.

Are over-the-counter medications and supplies covered by FSA?

Yes, many are. Pain relievers, allergy medicine, bandages, and first aid supplies are may be able to access. Vitamins and supplements are generally not, unless prescribed by a doctor. Check your plan's list of may be able to access expenses or ask your FSA provider if you're unsure about a specific item.

What if I overestimate and have money left over?

You lose it, unless your plan offers a grace period. That's why starting with a conservative estimate is safer than trying to maximize your contribution. The tax savings on a smaller amount you'll definitely spend beats the risk of forfeiting a larger amount.

How do I know what medical expenses are coming this year?

Review your calendar and insurance statements. Count regular prescriptions, scheduled appointments, and any procedures you know about. Ask your dentist or eye doctor if they have work planned. Don't guess about emergencies or rare events — stick to what you reasonably expect to happen.