December FSA Spend-Down: What Your Bills and EOBs Will Actually Reimburse
August 20, 2026 · Published by Soxoa
Put this guide into practice
See representative Medical Bill fields, compare the output with the source, then choose the workflow you need.
Every December, a predictable thing happens: people with an expiring FSA balance go shopping. And a lot of that shopping is unnecessary, because the reimbursable expenses were already sitting in a pile of unopened mail.
Before you buy anything, check what you already owe.
Use the right number
The single most common reason a claim comes back rejected is submitting the wrong figure off the paperwork.
A medical bill and its EOB carry at least four numbers:
- Billed charge — what the provider asked for. Frequently several times the real cost. Not your number.
- Allowed amount — the negotiated rate the plan and provider agreed on.
- Plan paid — the insurer's share.
- Patient responsibility — what is left for you.
Patient responsibility is the reimbursable amount. On an EOB it is often labelled "you may be billed." Submit the billed charge and you are asking to be reimbursed for money nobody is going to collect.
"Incurred," not "paid"
For a health FSA, the expense has to be incurred during the plan year — meaning the care was provided in that window. Whether you have paid the provider yet is a separate question.
That cuts two ways, and both are useful in December:
- A bill for care you received in November is reimbursable, even if you are still paying it off in March.
- Prepaying in December for a procedure scheduled in February is not reimbursable against this year's balance. The care has not happened.
Where the money usually is
If you are hunting for reimbursable expenses, look here before you look at a shopping cart:
Already incurred, probably in a drawer
- Copays and coinsurance from visits earlier in the year
- Amounts applied to your deductible
- Dental work — cleanings, fillings, crowns, orthodontia
- Therapy and mental health care
- Chiropractic and physical therapy
- Prescriptions, including refills you paid cash for
Genuinely useful, and eligible
- Eye exams, prescription glasses and sunglasses, a year of contact lenses
- Over-the-counter medicine — eligible without a prescription since the CARES Act
- Sunscreen SPF 15+, first aid supplies, menstrual products
- Medical devices: blood pressure monitors, thermometers, braces, CPAP supplies, hearing aids
Durable equipment deserves a specific mention. If you have a large balance and no pending bills, a blood pressure monitor or a hearing aid is a better use of the money than a drawer full of things you will not open.
What gets denied
Health insurance premiums. Unmistakably a medical cost, and categorically not reimbursable from a health FSA. This one catches people every year.
Everyday toiletries. Shampoo, toothpaste, soap, deodorant, makeup.
Cosmetic procedures, unless they correct a deformity arising from a congenital abnormality, injury or disease.
The middle category: get the letter first
Vitamins and supplements, gym memberships, and weight-loss programs are dual-purpose — they can be medical or they can be ordinary living, depending on why you are buying them.
They become reimbursable with a letter of medical necessity: a short note from a licensed provider naming the diagnosed condition, the item or service recommended, and the expected duration of treatment.
Get it before you submit the claim. Chasing a letter after a denial, in the last week of December, is a bad plan. Two exceptions worth knowing: prenatal vitamins are eligible without a letter, and a weight-loss program prescribed to treat a diagnosed disease such as obesity or hypertension qualifies where a general wellness program does not.
Two deadlines, not one
Your plan has a spending deadline — the last day to incur an expense — and a claim deadline, the last day to submit paperwork for expenses already incurred. They are different dates, and the claim deadline is usually later.
Which means: if the care happened before the spending deadline, you have not missed anything yet. Find the bills and file.
Do it faster
Paste your line items into the free FSA and HSA eligibility checker and it sorts them into reimbursable, needs-a-letter, and will-be-denied, with totals against the balance you are trying to clear. If you are not sure what that balance is, the FSA forfeiture calculator works it out from your pay stub.
General information, not tax or benefits advice. Your plan administrator has the final say on any specific claim; IRS Publication 502 governs what counts as a medical expense.