The Health Care FSA is one of the most common tax-advantaged benefits in U.S. employment and also one of the most consistently misunderstood by the employees who use it. It offers real tax savings: employees save roughly 25-30% on every dollar they route through it thanks to the combined federal, state, and FICA tax exclusion. But the use-it-or-lose-it rule still trips up workers every year, and the 2026 rule changes (a higher contribution limit, an updated carryover ceiling) are not yet reflected in most employee benefits communications. IRS data shows roughly 35 million U.S. employees participate in an FSA each year, and the average election is well below the IRS ceiling.
How a Health Care FSA Actually Works At open enrollment, employees elect an annual contribution amount up to the IRS limit ($3,400 for 2026). That amount is deducted in equal pieces from each paycheck, before federal income tax, FICA, and (in most states) state income tax. The employer typically partners with a third-party administrator that issues an FSA debit card or processes reimbursement claims.
The key feature, and the source of most employee confusion, is uniform coverage: on January 1, the employee can spend the full annual election immediately, even though only one pay period of contributions has been deducted. If the employee leaves mid-year after spending the full election, the employer eats the difference under IRS rules.
What's the Difference Between an FSA and an HSA? FSAs are employer-sponsored and use-it-or-lose-it. Retirement-plan-like rollover doesn't apply. HSAs are individual accounts tied to a high-deductible health plan, are fully portable, and roll over indefinitely. HSA contributions are also eligible for both employee and employer funding. The tax treatment is broadly similar, but the portability and carryover differences are significant.
The Use-It-or-Lose-It Rule and 2026 Carryover Under IRS rules, FSA funds not used by the end of the plan year are forfeited to the employer. To soften this, the IRS allows employers to offer one of two relief mechanisms. A carryover of up to $680 to the next plan year for 2026. Or a 2.5-month grace period after year-end during which prior-year funds can still be spent. An employer can offer one, not both.
Choosing between carryover and grace period is usually a participation calculation. Carryover encourages employees to elect more aggressively because they lose less. Grace periods sometimes work better for populations with irregular medical spending patterns.
What Qualifies as a Reimbursable Medical Expense Qualified expenses are defined in IRC 213(d): medical, dental, and vision care not covered by insurance, prescription drugs, and many medical devices. The 2020 CARES Act permanently restored OTC medications and menstrual products as eligible. Gym memberships, cosmetic procedures, and elective wellness items generally remain ineligible.
Documentation is the operational pain point. FSA debit card transactions at pharmacies and physician offices often auto-substantiate, but many transactions require receipts or a letter of medical necessity. The IRS Publication 502 is the authoritative list of qualified medical expenses.
Running a Health Care FSA Program Cleanly in 2026 The mechanics of FSA administration are mostly the third-party administrator's job, but HR owns the communication layer. Update open enrollment materials to reflect the 2026 limits. Explain the use-it-or-lose-it rule clearly to new hires at onboarding , because surprise forfeitures are a top complaint at year-end. Choose carryover or grace period based on the data for your population. Remind employees quarterly about unused balances, not just in December. The FSA is one of the highest ROI benefits an employer offers, but only if employees actually use it, and that participation rate is the real measure of whether the program is working.
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