How an FSA Debit Card Works

An FSA card is a prepaid debit card issued by your FSA plan to spend contributions on eligible medical expenses at approved merchants.

Sep 22, 2026

7 minute read

Burst guide cover, for shoppers: the headline "How an FSA Debit Card Works" over the line "The card is one way to pay. Reimbursement is the other." with three tags: Where it works, Why it declines, Get reimbursed.

Short answer

An FSA card is a prepaid debit card issued by your FSA plan administrator that lets you spend your pre-tax contributions on eligible medical expenses. It works at pharmacies, doctors' offices, hospitals, and retailers like CVS and Walgreens. Unlike a regular debit card, it only works for qualified purchases and declines otherwise.

The card is convenient because you don't have to pay out of pocket and wait for reimbursement afterward. But if the card declines, you can still pay with any card and get reimbursed. With a letter of medical necessity, many purchases that the card rejects as ineligible can be reimbursed afterward.

What the card is and who issues it

An FSA card is a prepaid debit card that holds the balance in your FSA account, minus any claims you've already made. HealthCare.gov describes an FSA as "an arrangement through your employer that lets you pay for many out-of-pocket medical expenses with tax-free dollars". The card is how you spend that money at checkout, instead of paying out of pocket and filing a claim afterward. Your FSA plan administrator issues the card. Some plans issue it automatically when you enroll. Others mail it after your first contribution. The card works only as long as you have an active FSA account with your employer.

How the balance works

The card's balance equals your FSA contribution for the year minus any money you've already spent. If you contribute $3,000 for the year and spend $1,200, your balance is $1,800. The balance goes down every time you use the card. Many plans also let you see your balance online or by phone, though some take a day or two to update after a transaction.

Where it works and where it does not

FSA cards work at many pharmacies, doctors' offices, hospitals, medical supply stores, and some retail chains. But not every store accepts FSA cards, and the ones that do may have restrictions. A pharmacy like CVS or Walgreens will accept the card for over-the-counter medications and medical supplies. A grocery store usually won't, even if it has a pharmacy section.

Common places the card works

Pharmacies and drugstores.
Doctor and dentist offices.
Hospitals and urgent care centers.
Optical shops and optometrists.
Medical supply and equipment stores.
Some health-focused retailers.

Why the card declines at some merchants

The administrator's system checks the merchant's category code when you use the card. If the code doesn't match a medical category, the card declines. That's why the card might work at one drugstore but not a grocery store, or at one retailer but not another. The merchant's payment processor, not the retailer itself, determines what category code it has.

Why it declines even for eligible items

The most common reason an FSA card declines for an eligible purchase is that the store's merchant code doesn't match the FSA system's approved categories. A drugstore will accept the card for pain relievers and bandages. But a big box retailer might not, even if the exact same items are sitting on the same shelf a few blocks away. The system doesn't check what you're buying. It only checks where you're buying it from.

Insufficient balance

Your FSA card can also decline if your balance is lower than the transaction amount. If you have $50 left and you try to buy $75 worth of supplies, the card will decline. Some plans let you swipe the card twice to split the transaction.

Ineligible items

Even at a medical merchant, the card can decline if the system flags the item as ineligible. Over-the-counter medications like cold medicine and pain relievers normally work. But cosmetic products, vitamins, and general wellness items typically don't, because they aren't qualified medical expenses under IRS rules on their own.

What to do instead: pay any way you like, then get reimbursed

When your FSA card declines, the simplest solution is to pay with your regular debit card, credit card, or cash instead. Keep your receipt. Many plans let you request reimbursement afterward through a website or app, and the administrator pays you out of your account by deposit or check.

The letter of medical necessity option

If the item you bought isn't normally eligible, you may still get reimbursed with a letter of medical necessity. This letter, written by a licensed clinician, connects a diagnosed medical condition to the purchase. A yoga mat is reimbursable with a letter when a clinician ties it to a condition such as chronic back pain. Nothing else about the purchase changes. The letter has to be dated on or before the purchase, so request it before you buy if you can.

Burst files the reimbursement claim with your FSA, HSA or HRA administrator after you've got the letter. The administrator pays you out of your account by deposit or check.

Balance, activation, and lost card: the practical answers

Once you've got an FSA card, three practical questions come up most often: how to check your balance, how to activate the card, and what to do if you lose it.

Checking your balance

Your FSA administrator should give you a way to check your balance online, by phone, or through a mobile app. The website or app also usually shows your spending history and pending claims. If you don't know how to access it, your plan administrator's website should have instructions. Some plans email you a statement once a month.

Activating your card

Many FSA cards arrive pre-activated and ready to use. Others require you to activate them online or by phone before the first use. Your plan administrator should include activation instructions with the card. If you lose your card or it expires, you can usually request a new one through the plan website or by calling customer service.

What happens to money you do not spend

FSA money is subject to use-it-or-lose-it: whatever you don't spend by the end of the plan year is forfeited, unless your plan adds a grace period or a carryover. For plan years starting in 2026, the IRS says "the maximum carryover amount is $680, an increase of $20 from tax years beginning in 2025". Check your plan document to see whether your employer adopted that carryover, a grace period, or neither. HSA and HRA balances carry over with no deadline. Check your plan document or call your administrator to see which rules apply to your account.

Getting it reimbursed with Burst

Here's the practical route. Request a letter of medical necessity from Burst ($35 once, about two minutes). A licensed clinician reviews it and it's typically in your inbox within 24 hours. Burst files the reimbursement claim with your FSA, HSA or HRA administrator, who pays you out of your account by deposit or check. If there's no letter there's no charge, and a denied claim means your money back. The letter has to be dated on or before the purchase it covers, so do this step first.

Request my letter for $35

Frequently asked questions

What is an FSA card?

An FSA card is a prepaid debit card issued by your FSA plan administrator that holds your pre-tax contributions. You use it to pay for eligible medical expenses without filing a claim.

Why did my FSA card decline?

Common reasons include the store's merchant code not matching the FSA system's approved categories, insufficient balance, or the item being ineligible. Pay with another card and request reimbursement instead, or get a letter of medical necessity if the item is medically necessary.

Can I use my FSA card anywhere?

FSA cards work at pharmacies, doctors' offices, hospitals, and some retailers, but not everywhere. Grocery stores, department stores, and online retailers often don't accept them even for medical items.

What happens if I do not spend my FSA money?

FSA is subject to use-it-or-lose-it: money you don't spend by the end of the plan year is forfeited unless your employer adds a grace period or carryover. IRS Publication 969 confirms "coverage during a grace period by a general purpose health FSA is allowed if the balance in the health FSA at the end of its prior-year plan is zero". Ask your administrator which option your plan uses.

Can I get reimbursed if I do not use my card?

Yes. Pay with any card, keep your receipt, and request reimbursement afterward. If the purchase needs a letter of medical necessity, Burst files that claim with your administrator once you have the letter.

How long does reimbursement take?

Timing depends on your plan administrator, so check your plan's portal for status. For purchases that need a letter of medical necessity, Burst typically delivers the letter within 24 hours of your request.

Keep reading: What is an FSA, What you can buy with an FSA, HSA vs. FSA, and all guides on this topic.