Flexible Spending Accounts vs. Health Savings Accounts

How each account is structured

A Flexible Spending Account (FSA) is an employer-sponsored benefit. Your employer sets up the account, you elect an annual contribution during open enrollment, and the funds are withheld pre-tax from each paycheck. The IRS sets the annual contribution limit, which adjusts periodically. One distinct feature: the full elected amount is available to you on day one of the plan year, even before all contributions have been deducted.

A Health Savings Account (HSA) is owned by the individual. You open one through a bank, credit union, or benefits administrator, and contributions can come from you, your employer, or both. Funds grow tax-free and can be invested in mutual funds or similar vehicles once the balance exceeds a threshold set by the account provider. The IRS publishes annual contribution limits for HSAs separately from FSA limits. For current figures, the IRS website is the authoritative source.

For a deeper look at HSA mechanics, see the guide to how HSAs work and who qualifies.

Eligibility rules that determine your options

FSA eligibility is tied to employment. If your employer offers one as part of its benefits package, you can generally enroll during open enrollment or a qualifying life event. You do not need a specific type of health insurance plan to participate in a standard health FSA, though you cannot contribute to both a standard FSA and an HSA at the same time. A limited-purpose FSA (covering only dental and vision) is an exception that can coexist with an HSA.

HSA eligibility has a strict prerequisite: you must be enrolled in an HSA-qualifying High-Deductible Health Plan (HDHP). The IRS defines minimum deductible and maximum out-of-pocket thresholds that a plan must meet to qualify. You also cannot be claimed as a dependent on someone else's tax return or be enrolled in Medicare. These rules make HSAs unavailable to a portion of employees whose plans do not meet HDHP criteria.

Understanding how your health plan interacts with these accounts connects directly to deductible and cost-sharing rules. The common myths about health insurance deductibles article addresses frequent misunderstandings there.

Rollover rules and what happens to unused funds

The FSA's use-it-or-lose-it rule is its most discussed limitation. Under IRS rules, unused FSA balances generally do not carry over to the next plan year. Employers may offer one of two exceptions: a grace period (up to 2.5 months into the new plan year to spend remaining funds) or a carryover of a limited amount set by the IRS. Employers are not required to offer either option, so the default for many plans remains full forfeiture at year-end.

HSA balances roll over indefinitely. There is no deadline to spend funds, no employer-granted grace period needed, and no annual forfeiture risk. This makes the HSA well-suited to building a reserve for larger future expenses or for healthcare costs in retirement. The account also retains its tax advantages through investment growth, a feature FSAs do not provide.

Tax treatment and contribution mechanics

Both accounts reduce taxable income, but through slightly different mechanisms. FSA contributions are deducted pre-tax from payroll, meaning they reduce your gross income for federal income tax and FICA (Social Security and Medicare) purposes. HSA contributions made through payroll also avoid FICA taxes. Contributions made directly to an HSA outside of payroll are deductible on your federal income tax return, though they do not avoid FICA in that case.

HSA withdrawals for qualified medical expenses are tax-free at any age. After age 65, non-medical withdrawals are taxed as ordinary income (similar to a traditional IRA) but are not subject to the additional 20% penalty that applies before 65. FSA withdrawals for qualified expenses are also tax-free, but the account has no investment component and no analogous flexibility after a certain age.

Both accounts can be used for a broad range of qualified medical expenses as defined by the IRS, including prescriptions, copays, dental, and vision care. Preventive services covered at no cost under the ACA generally do not require spending from either account. See which preventive services are covered under the ACA for a breakdown of those benefits.

If you face out-of-pocket bills after using these accounts, strategies for negotiating medical bills may further reduce your costs.

This article is for general informational purposes only and is not financial or medical advice. Tax rules change and individual circumstances vary. Consult a qualified tax professional or financial adviser before making decisions about health account contributions or enrollment.