How Does an FSA Work? A Plain-English Guide to Flexible Spending Accounts

A Flexible Spending Account (FSA) works like a pre-tax savings envelope your employer sets up for you: you decide how much to put in for the year, that money comes out of your paycheck before taxes, and you spend it on eligible medical or dependent care costs. The catch is you generally have to use it within the plan year, and you can't take it with you if you leave your job. That's the whole idea in one breath. But there's a lot of nuance underneath it, so let's walk through the parts that actually matter when you're deciding how much to put in.

What exactly is an FSA and why would I want one?

An FSA is an employer-sponsored account that lets you set aside part of your paycheck, tax-free, to cover health care costs or dependent care costs. There are two main types: a Health Care FSA (also called a Medical FSA) that covers things like copays, prescriptions, and dental work, and a Dependent Care FSA that covers daycare, preschool, or care for an aging parent so you can work.

The appeal is simple: every dollar you put into an FSA skips federal income tax, Social Security tax, and Medicare tax. If you're in the 22% federal bracket, a $2,000 FSA contribution could save you somewhere around $450 to $600 depending on your state taxes too. You're not getting free money, but you are getting to pay for expenses you'd have anyway with money the government never taxed.

Employers like FSAs because they're relatively cheap to offer compared to richer benefits, and they help employees stretch their take-home pay a little further without the company footing a big new bill.

How does the money actually move from my paycheck to my expenses?

Here's the mechanic that surprises a lot of first-time enrollees: with a Health Care FSA, you get access to your full annual election on day one of the plan year, even though you haven't contributed all of it yet through payroll. If you elect $2,400 for the year, that entire amount is available to you in January, and your employer deducts it from your paycheck in equal installments the rest of the year, usually $100 per paycheck if you're paid semi-monthly.

This is different from a Dependent Care FSA, where you can typically only use money that's already been deducted from your paycheck, not the full annual amount up front.

Who actually runs the account?

Your employer sets up the plan, but they almost never administer it themselves. That job usually goes to a Third Party Administrator (TPA), who handles the debit card, processes claims, checks receipts for IRS compliance, and answers your questions when a charge gets flagged. Your HR team picks the plan design; the TPA runs the day-to-day.

How much can I actually put into an FSA?

The IRS sets an annual cap on Health Care FSA contributions, and it gets adjusted most years for inflation. According to IRS Revenue Procedure 2025-32, the 2026 Health Care FSA contribution limit is $3,400 per employee, up from $3,300 in 2025. That limit applies per person, so a married couple who each have access to their own employer's FSA can each contribute up to the limit separately.

The Dependent Care FSA works differently. Its cap isn't indexed to inflation the same way; it's set by statute under Internal Revenue Code Section 129, and per IRS Publication 503, it's capped at $5,000 per household for most filers, or $2,500 if you're married and filing separately. That number has stayed at $5,000 since the mid-1980s except for a temporary bump to $10,500 in 2021 under the American Rescue Plan, which expired after that one year.

A few things worth knowing about limits:

●Employers can set a lower cap than the IRS maximum. If your plan document says $2,500, that's your ceiling even though the IRS allows more.

●The limit is per employee, not per household, for Health Care FSAs, but it is per household for Dependent Care FSAs.

●You can't change your election mid-year unless you have a qualifying life event like marriage, divorce, birth of a child, or a change in employment status.

What can I actually buy with FSA money?

The IRS keeps a fairly detailed list of what counts as a qualified medical expense under Section 213(d) of the tax code, and your TPA's substantiation process checks purchases against it. Broadly, eligible items include:

●Doctor, dentist, and vision copays and deductibles

●Prescription medications

●Over-the-counter medicines like pain relievers, allergy pills, and cold remedies

●Menstrual care products

●Contact lenses, glasses, and LASIK surgery

●Physical therapy and chiropractic care

●Hearing aids and hearing aid batteries

That over-the-counter drug piece is worth flagging because it changed fairly recently. Before 2020, you needed a doctor's prescription to use FSA money on OTC medicine. The CARES Act of 2020 permanently removed that prescription requirement and also added menstrual care products to the eligible list. So if you're going off old information, you might think you need a note from your doctor for allergy medicine, and you don't anymore.

What's not eligible? Cosmetic procedures, gym memberships, general wellness supplements, and health insurance premiums are typically excluded. Vitamins are a gray area unless a doctor recommends them for a specific condition, in which case a Letter of Medical Necessity can sometimes make them eligible.

What happens to money I don't spend by the end of the year?

This is the part people worry about most, and it's usually called the use-it-or-lose-it rule. Technically, if your plan offers no extensions, any money left in your Health Care FSA at the end of the plan year gets forfeited back to the plan. But most employers soften this with one of two options, and they can only pick one, not both:

Grace period

A grace period gives you extra time after the plan year ends to spend down last year's balance. Under IRS Notice 2005-42, the maximum grace period an employer can offer is two and a half months, so if your plan year ends December 31, you'd have until March 15 to spend the remaining funds.

Carryover

A carryover lets you roll over a limited amount into the next plan year without any deadline pressure. The carryover cap moves with the contribution limit; it's set at 20% of the maximum annual Health Care FSA contribution. For 2026, that puts the carryover max at $680, following the increase in the 2026 contribution limit to $3,400 under IRS Revenue Procedure 2025-32.

Run-out period

Separate from both of those, many plans also offer a run-out period, typically 60 to 90 days after the plan year ends, during which you can still submit claims for expenses you incurred during the plan year, even though you can't incur new expenses anymore. Don't confuse a run-out period with a grace period; one lets you file old paperwork, the other lets you spend on new purchases.

Here's a quick side-by-side to keep these straight:

●Grace period: extends spending by up to 2.5 months into the new year

●Carryover: rolls up to $680 (2026 figure) into next year with no time limit on when you spend it

●Run-out period: lets you submit claims for last year's already-incurred expenses, usually 60 to 90 days

Dependent Care FSAs generally aren't eligible for the carryover option, though they can offer a grace period, so check your specific plan document rather than assuming.

How is an FSA different from an HSA?

People mix these up constantly, and the differences actually matter for your wallet. Here's the short version:

●Eligibility: An HSA requires you to be enrolled in a High-Deductible Health Plan (HDHP). An FSA has no such requirement and works alongside almost any health plan.

●Ownership: HSA funds are yours forever, even if you switch jobs or retire. FSA funds generally belong to the employer's plan if you leave before spending them.

●Rollover: HSAs have no use-it-or-lose-it rule at all; the full balance rolls over every year indefinitely. FSAs only roll over up to the carryover cap, or expire under the grace period rules described above.

●Contribution limits: HSA limits are higher and adjusted separately by the IRS each year, and they're published alongside the FSA limits.

●Who can contribute: Both employees and employers can contribute to either account, but only HSAs allow employees to keep contributing after age 65 as long as they're not enrolled in Medicare.

You generally can't have a full Health Care FSA and an HSA at the same time, though a Limited Purpose FSA that covers only dental and vision expenses can work alongside an HSA.

Why do employers hire a TPA to run this instead of doing it in-house?

Running an FSA correctly means tracking IRS substantiation rules, verifying every debit card swipe against an eligible expense list, managing grace periods or carryovers without violating the uniform coverage rule, handling COBRA continuation for FSA balances when someone leaves mid-year, and generating nondiscrimination testing so the plan doesn't accidentally favor highly compensated employees. That's a lot of moving parts for an HR team that's also handling open enrollment, onboarding, and every other benefit on the table.

A Third Party Administrator like CafeHealth takes that operational weight off HR's plate. That means employees get a debit card that works at the point of sale, a portal to check balances and submit claims, and someone to call when a receipt gets rejected instead of guessing why. It also means the employer isn't personally liable for interpreting every gray-area IRS ruling on eligible expenses, because the TPA is staying current on that so the plan documents and day-to-day administration match what the IRS actually allows.

If you're an HR leader or broker weighing whether to bring in outside help for FSA administration, or you want a second opinion on your current setup, CafeHealth's FSA administration services are built specifically around taking that burden off your internal team while keeping the employee experience simple.

If you'd rather just talk it through, book a free consultation with Shannon and she'll walk you through what makes sense for your specific plan, your headcount, and your renewal timeline. No pressure, just a real conversation about what FSA administration should look like for your company.

Quick Questions People Actually Ask

What is the FSA contribution limit for 2026?

The 2026 Health Care FSA limit is $3,400 per employee, according to IRS Revenue Procedure 2025-32. That's up $100 from the 2025 limit of $3,300. The Dependent Care FSA limit stays at $5,000 per household since that cap is set by statute, not inflation adjustment.

How does a flexible spending account work?

You pick a dollar amount during open enrollment, it gets deducted from your paycheck in equal chunks before taxes are calculated, and you use that money (often through a debit card) on eligible medical or dependent care expenses throughout the plan year. With a Health Care FSA, you can typically access your whole annual election starting day one, even though your paycheck deductions haven't caught up yet.

What happens to unused FSA money at the end of the year?

It depends on your employer's plan design. If they offer a grace period, you get up to 2.5 extra months to spend it. If they offer carryover, you can roll over up to $680 (for the 2026 plan year) into next year with no deadline. If your plan offers neither, unspent money is forfeited under the use-it-or-lose-it rule, so it's worth checking your specific plan document.

Can I use my FSA to buy over-the-counter medicine?

Yes. Since the CARES Act of 2020, you no longer need a doctor's prescription to use FSA funds on over-the-counter medications like pain relievers, allergy pills, or cold medicine. That same law also made menstrual care products eligible, which wasn't the case before.

What is the difference between an FSA and an HSA?

The biggest differences are ownership and rollover rules. An HSA is yours permanently, even after you leave a job, and the full balance rolls over every year with no expiration. An FSA generally belongs to your employer's plan if you leave before spending it, and it's subject to the use-it-or-lose-it rule unless your plan offers a grace period or limited carryover. HSAs also require you to be enrolled in a High-Deductible Health Plan, while FSAs don't have that requirement.

Can I change my FSA contribution amount in the middle of the year?

Generally no. FSA elections are locked in for the plan year once open enrollment closes, because the IRS wants to prevent people from adjusting contributions based on expenses they already know are coming. The exception is a qualifying life event, like getting married, having a baby, getting divorced, or a change in employment status, which opens a special enrollment window to adjust your election.