Flexible Spending Accounts: Rules, Limits, and Smart Uses

The Tax Break You Have to Use to Keep

Flexible Spending Accounts offer a meaningful tax advantage on predictable expenses — but unlike an HSA, they come with a strict deadline. Unused FSA funds are forfeited at year-end (with limited exceptions), a rule sometimes called "use it or lose it." That single feature shapes everything about FSA strategy. Contribution decisions must be made before the plan year begins, based on projected expenses, with virtually no ability to adjust mid-year. Getting this right saves hundreds to thousands of dollars. Getting it wrong means voluntarily handing money back to the employer or plan administrator. Understanding the product before open enrollment is mandatory.

Two Types of FSAs: Medical and Dependent Care

Health FSA (Medical FSA) — covers qualified medical, dental, and vision expenses for the employee, spouse, and dependents. Established under IRS Section 125 as part of an employer's cafeteria plan. Contributions reduce federal income tax, Social Security tax, and Medicare tax (a combined effective rate of 30–40% for most employees).

Dependent Care FSA (DC-FSA) — covers qualifying dependent care expenses: daycare, after-school programs, summer day camps, and adult day care for elderly or disabled dependents. Distinct from the Child and Dependent Care Tax Credit, though the two interact. Most households cannot claim both the full DC-FSA exclusion and the tax credit for the same expenses.

2024 Contribution Limits

For the Health FSA, the $3,200 limit is per employee, not per family. A couple where both spouses have employer FSA plans can each contribute $3,200, for a household total of $6,400.

Eligible Expenses: Health FSA

The IRS defines qualified medical expenses in Publication 502. The list is broader than most people realize:

• Prescription medications and insulin
• Medical, dental, and vision insurance deductibles, copays, and coinsurance
• Glasses, contact lenses, and contact lens solution
• Hearing aids and batteries
• Orthodontia and dental procedures
• Menstrual care products (explicitly added by the CARES Act of 2020)
• Over-the-counter medications (cold remedies, antacids, pain relievers — also CARES Act 2020)
• Mental health therapy and psychiatric care
• Sunscreen (SPF 15+) and acne treatments
• Smoking cessation programs and products
• Fertility treatments

Cosmetic procedures, gym memberships, vitamins (unless prescribed for a medical condition), and teeth whitening are not eligible.

The Use-It-or-Lose-It Rule and Its Exceptions

Under the base IRS rules, unused Health FSA funds are forfeited at the plan year's end. Two relief mechanisms exist, but employers choose whether to offer them — neither is mandatory:

• Carryover option — employers may allow employees to carry over up to $640 (2024 limit; inflation-adjusted) of unused funds into the next plan year; this amount is added to the following year's contribution limit
• Grace period option — employers may provide a grace period of up to 2.5 additional months (until March 15 for calendar-year plans) during which employees can spend the prior year's unused funds

Employers can offer the carryover OR the grace period — not both simultaneously. Many employers offer neither. Employees should review their plan documents or ask HR to determine which option, if any, applies to their specific plan.

The Uniform Coverage Rule: An Often-Missed Advantage

The Health FSA's uniform coverage rule is one of its most valuable features. The full annual election amount is available from the first day of the plan year — even though contributions are made in equal installments throughout the year. An employee who elects $3,200 and has a $3,200 medical expense in January can submit the claim and receive full reimbursement immediately, even though only one-twelfth of the total contribution has been deducted from their paycheck. If that employee then leaves the job, the employer cannot recover the funded-but-not-yet-contributed difference. This is the opposite of an HSA, where only what has been contributed is available.

Dependent Care FSA: Different Rules Apply

Unlike the Health FSA, the DC-FSA follows a cash-available model: only amounts already contributed to the account can be reimbursed. There is no uniform coverage rule. The dependent care expenses must also be incurred so that the taxpayer (and spouse, if married) can work or actively look for work — expenses incurred while a spouse is not working (except for a full-time student or disabled individual) are not eligible.

The interaction with the Child and Dependent Care Tax Credit is nuanced: expenses reimbursed through the DC-FSA reduce the expenses eligible for the tax credit. For high earners, the DC-FSA's income tax exclusion is generally more valuable than the credit, which phases down significantly above $15,000 in income. For lower-income earners, the credit may be worth more. This article is for informational purposes only and does not constitute financial advice.