Here is a rule almost nobody explains, and it is the single most useful thing to know before you settle on a health FSA election at open enrollment.
If you elect $3,000 in a health flexible spending account, the entire $3,000 is available to you on the first day of the plan year, even though your payroll deductions have contributed roughly $115 of it. Spend all $3,000 in January on dental work, and the plan reimburses you all $3,000. Then, if you leave that job in February, the employer generally absorbs the difference and cannot come after you for it.
That is the uniform coverage rule, and it comes from the IRS cafeteria plan regulations under section 125. Every article on health FSA election tells you to add up your predictable expenses and not to over-elect. None of them mentions that the risk in this account runs in two directions and that one of those directions favors you.
Two rules govern your health FSA election, not one
The 2026 limits come from IRS Revenue Procedure 2025-32. You can elect up to $3,400 in a health FSA, and your plan may allow up to $680 of unused money to carry into 2027.
That carryover figure matters more than the headline limit, because it is the difference between a hard forfeiture cliff and a soft one. And here is the part people get wrong: carryover and a grace period are mutually exclusive. Your employer can offer a carryover of up to $680, or a grace period of up to two and a half extra months to incur expenses, or neither. It cannot offer both. So the first question is not how much to elect, it is which of those two your plan has, because they call for different elections.
With a $680 carryover, electing $680 above your confident spending is nearly risk-free. With a grace period instead, you get extra time but no dollars survive past it. With neither, every dollar you do not spend by December 31 is gone.
Separately, note the run-out period, which is different from both. That is the window after the plan year closes to submit claims for expenses you already incurred during the year. It does not let you incur new expenses. People conflate run-out with grace period and lose money doing it.
How much is actually forfeited
EBRI analyzed 3.2 million flexible spending accounts and found that roughly half of accountholders forfeited something, with an average forfeiture of about $436 in 2023.
Read that carefully. Half of people lose nothing. The average loss among all accountholders is $436, which means the typical person who forfeits is losing a few hundred dollars rather than thousands.
Now weigh that against the tax saving. FSA contributions come out through a cafeteria plan, so they escape federal income tax, Social Security tax and Medicare tax. At a 22% federal bracket plus 7.65% in payroll tax, you are saving 29.65% on every dollar, plus state tax where applicable.
On a $2,000 election at roughly 30%, the tax saving is about $600. If your realistic worst case is forfeiting $436, you are still ahead by well over $150 even in the bad scenario. That asymmetry is why the standard advice to elect conservatively is more cautious than the arithmetic requires.
The worked example
Say you can confidently predict the following for next year: two dental cleanings and a filling at around $600, an eye exam and glasses at around $300, three specialist copays at around $150, and monthly prescription copays totaling around $480. That is about $1,530 of near-certain spending.
Elect $1,530 and you save roughly $459 in tax at a 30% combined rate, with essentially zero forfeiture risk.
Elect $2,200 instead, adding a cushion for the things you cannot predict, and you save roughly $660. If your plan has the $680 carryover and you only spend $1,530, the $670 difference carries forward and you lose nothing. If your plan has no carryover and you spend nothing extra, you forfeit $670 against a $660 tax saving, so you break roughly even on the cushion.
That is the actual shape of the decision. With carryover, aggressive is close to free. Without it, the cushion is roughly a coin flip and your confident baseline is the right number.
One eligibility trap
A general-purpose health FSA disqualifies you from contributing to a health savings account. IRS Publication 969 is explicit about this, and it catches people who switch to a high-deductible plan while still sitting inside an FSA grace period, because grace-period funds keep you ineligible until the grace period ends.
If you are moving to an HDHP with an HSA for next year, spend your FSA down to zero by December 31 and check whether your plan’s grace period extends your ineligibility into the new year.
Also worth knowing: the dependent care FSA is a completely separate election with its own limit, and it has no carryover. For 2026 the dependent care limit rose substantially under the One Big Beautiful Bill legislation, to a figure widely reported as $7,500, though I would confirm the exact number against your plan documents or IRS guidance directly rather than trusting a summary, including this one.
What to do this week
Open your benefits portal and find three things before you type a number: whether your plan offers carryover or a grace period or neither, the deadline for each, and the run-out period for submitting claims.
Then build your election in two layers. The bottom layer is what you are confident you will spend, which for most households is prescriptions, planned dental, vision, and routine copays. The top layer is a cushion sized to your carryover, if you have one, and to zero if you do not.
And if you are anticipating a job change, remember which way the uniform coverage rule runs. Front-loading a large expense early in the plan year is not gaming anything. It is exactly how the regulation is written, and it is the reason a health FSA election carries less downside than the forfeiture warnings suggest. If you are also choosing between plan types, the HDHP versus PPO math has to come first because it determines whether you can use an FSA at all, and timing care around your out-of-pocket maximum affects how much you will actually spend.
