Yes, you can use your FSA for bills from a previous year, as long as the medical care itself happened during that plan year and you file the claim before your plan’s run-out period ends. The IRS ties FSA reimbursement to the date the service was provided, not the date the bill arrives or the date you pay it.1Internal Revenue Service. Publication 502 (2025), Medical and Dental Expenses What you cannot do is pay an old bill with this year’s FSA money. The funds have to come from the account that was active when you received the care.
Why the Service Date Is the Only Date That Matters
Every FSA claim turns on a single question: when did the medical care actually happen? A procedure performed on November 3 belongs to that plan year even if the provider doesn’t send the bill until February. A prescription filled on December 28 belongs to that plan year even if you pay for it in January. The billing date, the payment date, and the date your insurance finishes processing the claim are all irrelevant for FSA purposes.
This is a real departure from how medical expenses work on your tax return. For itemized medical deductions, the year you paid controls. For FSA reimbursement, the year the expense was incurred controls.1Internal Revenue Service. Publication 502 (2025), Medical and Dental Expenses Mix those up and your claim gets denied.
The practical consequence: if your dentist filled a cavity in October and your insurance company takes until January to process the claim and send you a bill for the balance, that expense still belongs to the old plan year. You’d need remaining funds from that year’s account, or carryover dollars if your plan offers them, to cover it. Submitting it against the new year’s election will get the claim rejected.
The Run-Out Period Is Your Real Deadline
The reason previous-year bills are reimbursable at all is that most plans give you a window after the plan year ends to submit claims for care you received during it. This window is called a run-out period, and most employers set it at around 90 days. For a plan year ending December 31, that typically means you have until late March to gather receipts and submit reimbursement requests for the prior twelve months.
The run-out period only extends your filing deadline. It does not extend the window for receiving care. An expense incurred on January 15 of the new year cannot be filed against the old plan year’s funds during the run-out period. The point of a run-out is paperwork breathing room, nothing more.
Length varies by employer, because the IRS lets each plan set its own timeframe. Some run 60 days, others stretch to 120 days or longer. Check your Summary Plan Description for the exact date, and set a calendar reminder well before it arrives. Most people who forfeit FSA money don’t lose it because they lack eligible expenses. They lose it because they miss this cutoff.
Fiscal-year plans work the same way with shifted dates. If your plan year ends June 30, the run-out and any grace period slide accordingly.
Grace Periods and Carryovers Change the Math
Beyond the run-out period, the IRS permits two other mechanisms for handling leftover FSA money.2Internal Revenue Service. IRS: Eligible Employees Can Use Tax-Free Dollars for Medical Expenses Your employer can offer one but not both for the same FSA. Many employers offer neither, so don’t assume yours does.
Grace Period
A grace period gives you an extra two and a half months after the plan year ends to actually incur new medical expenses using the previous year’s leftover balance.3Internal Revenue Service. Publication 969 (2025), Health Savings Accounts and Other Tax-Favored Health Plans For a calendar-year plan, that usually means through March 15. This is different from a run-out period. A grace period extends the time to receive care. A run-out period only extends the time to submit paperwork.
When a grace period overlaps with a new plan year, the plan spends the oldest dollars first. If you have $200 left from the prior year and a $3,400 election for the new year, a February doctor visit uses the old $200 before touching the new balance.
Carryover
The carryover option rolls a portion of unused funds into the next plan year rather than extending the spending deadline. For the 2026 plan year, the IRS caps the carryover at $680.4Internal Revenue Service. Revenue Procedure 2025-32 Anything above that is forfeited, and your employer can set a lower cap. Carried-over funds merge into the new plan year’s balance and follow the same rules as new contributions. The 2025 carryover maximum was $660.5Internal Revenue Service. Revenue Procedure 2024-40
Carryover doesn’t reduce next year’s election limit. If your plan allows a $680 carryover and you elect $3,400 for 2026, you’d have up to $4,080 available.4Internal Revenue Service. Revenue Procedure 2025-32
Documentation for a Previous-Year Bill
Late-arriving bills require the same documentation as any other claim, but administrators scrutinize cross-year submissions closely, so the details matter. You need an itemized statement from the provider showing the patient’s name, the date of service, a description of the care, and the amount charged. A credit card receipt or bank statement will be rejected because it doesn’t identify the specific service.
If insurance covered part of the cost, include the Explanation of Benefits from your carrier. The EOB shows what insurance paid, what was applied to your deductible, and your out-of-pocket responsibility. Your FSA reimbursement cannot exceed what you actually owed after insurance adjustments.
Some expenses require a Letter of Medical Necessity, particularly items that straddle the line between medical and personal use like ergonomic equipment, air purifiers, or specialized mattresses.6FSAFEDS. Letter of Medical Necessity Form For dual-purpose items, you can only claim the additional cost above what a standard version would cost.1Internal Revenue Service. Publication 502 (2025), Medical and Dental Expenses
The most common reason previous-year claims are rejected is a mismatch between the billing date on a statement and the actual date of service. Providers sometimes print the date they generated the invoice rather than the date they saw you. If a claim is denied for this reason, contact the provider’s billing department and request a corrected itemized statement showing the true service date.
Filing the Claim Against the Right Plan Year
Most FSA administrators offer an online portal or mobile app for submitting claims. Log in, select the option for a manual claim, and choose the correct plan year for the expense. This step is critical for previous-year bills, because the system needs to pull funds from the right account. Upload your itemized statement and EOB, then certify that the expense hasn’t been reimbursed from any other source.7FSAFEDS. Health Care FSA – How to File a Claim for Approval
Processing typically takes up to five business days, after which you’ll get either an approval or a request for more documentation.7FSAFEDS. Health Care FSA – How to File a Claim for Approval Approved claims are usually paid by direct deposit or mailed check within a week. If you’re filing near the end of your run-out period, submit early enough to allow time for back-and-forth. A claim stuck in pending status when the run-out deadline hits can be denied regardless of its merits.
If the Claim Gets Denied
A denial isn’t the end. Under federal benefits regulations, you have at least 180 days from the date you receive a denial to file a formal appeal.8U.S. Department of Labor. Benefit Claims Procedure Regulation FAQs The denial notice explains why the claim was rejected and what you’d need to provide to overturn it.
The most fixable denials involve documentation gaps. If the administrator says the service date is unclear or the description is insufficient, request a corrected itemized bill from the provider and attach a brief written explanation identifying what was corrected. Denials based on the expense falling outside the plan year are harder to overturn, since the date-of-service rule leaves little room for interpretation. But if the administrator applied the wrong service date, a corrected provider statement can resolve that.
If your internal appeal is denied, your Summary Plan Description will outline further review steps. For plans governed by ERISA, you also have the right to request an external review or take the matter to the Department of Labor. Most FSA disputes resolve at the first appeal level once the right documentation is attached.
One Caveat If You’ve Changed Jobs
Leaving an employer changes what’s available to you. FSA coverage generally ends on your last day of employment or at the end of that month, and after that date you can no longer incur new expenses against the account. You typically still get a run-out period to file claims for care you received while covered, so a bill that arrives after you’ve left for a service that happened while you were still employed can still be reimbursed if you file in time. COBRA can sometimes extend an FSA past termination, but only in narrow circumstances where the account is underspent enough to justify paying premiums of up to 102% of the cost yourself.9U.S. Department of Labor. An Employee’s Guide to Health Benefits Under COBRA Run the numbers before electing it.