Both the FSA and the HSA are tax-advantaged accounts for healthcare expenses. They sound similar and people mix them up. They are actually very different, and the difference decides which one you should fund.
At a glance
| Feature | FSA (Flexible Spending Account) | HSA (Health Savings Account) |
|---|---|---|
| Who can have it | Anyone with an FSA-offering employer | Only people enrolled in an HSA-eligible high-deductible plan |
| Owner | Employer-sponsored (you fund it, employer holds it) | You own it personally |
| Portability | Stays with the employer when you leave | Goes with you forever |
| Rollover | Use it or lose it (with limited carryover or grace period at some employers) | Rolls over indefinitely |
| Investment | Usually no; cash only | Yes; can invest above a minimum balance at most providers |
| Annual contribution limit | Set annually by the IRS | Set annually by the IRS, higher than FSA |
| Tax treatment | Pre-tax contributions; no growth component | Pre-tax contributions, tax-free growth, tax-free qualified withdrawals |
| Effect on payroll taxes | Avoids FICA when contributed through payroll | Avoids FICA only when contributed through payroll |
| Spouse coordination | A regular FSA can disqualify a spouse HSA | A spouse FSA can disqualify your HSA |
Eligibility differences
This is the line that decides for most people.
FSA. Available if your employer offers it. No requirement about your medical plan. You can be on any plan that does not block FSA-eligible benefits.
HSA. Only available if you are enrolled in an HSA-eligible high-deductible health plan and have no other disqualifying coverage. Other disqualifying coverage includes a regular health FSA (yours or a spouse), Medicare enrollment in any part, VA care for non-service-connected conditions within the last three months, and being claimed as a dependent.
If you are eligible for both, you typically have to choose. A regular FSA disqualifies the HSA. A limited-purpose FSA, restricted to dental and vision, is the exception that can coexist with an HSA.
Ownership and portability
The HSA is yours. If you leave your job, the account comes with you. If you stop being HSA-eligible, you cannot contribute, but you keep the balance and can still spend it on qualified medical expenses tax-free.
The FSA is sponsored by your employer. Unused balances at the end of the plan year (after any carryover or grace period) usually go back to the employer. If you leave mid-year, you may forfeit what you have not spent, though COBRA-style continuation of the FSA exists in some plans.
The rollover rule
This is where the FSA bites people.
FSA. Use-it-or-lose-it by default. Employers have two IRS-permitted softeners: a carryover (a small dollar amount that moves to next year, set annually by the IRS) or a grace period (up to 2.5 months at the start of the next year to spend last-year money). An employer can offer one or the other, not both. The money still has a deadline.
HSA. No deadline. Money rolls over from year to year forever. The balance can grow into a substantial account if you contribute regularly and invest above a cash cushion.
The tax math
Both accounts reduce federal income tax on the contributions. Both also avoid FICA (Social Security and Medicare tax) when contributed through payroll.
The HSA adds two more tax benefits the FSA does not have.
Tax-free growth. Most HSA providers let you invest the balance once it exceeds a minimum (often a few hundred to a few thousand dollars). Investment gains inside the HSA are not taxed.
Tax-free qualified withdrawals. When you pay for a qualified medical expense from HSA funds, the withdrawal is not taxed. The IRS list of qualified expenses is in Publication 502 and is broad: deductibles, copays, prescriptions, dental, vision, therapy, long-term-care premiums up to a limit, COBRA premiums, and after 65 most Medicare premiums.
This makes the HSA the only account that gives you all three tax benefits: deductible going in, tax-free growth, and tax-free withdrawal. A 401(k) gives you the first. A Roth gives you the third. The HSA gives you all three for qualified medical use.
When the FSA makes more sense
You do not have an HSA-eligible plan and your employer offers an FSA.
You can predict your annual medical spend reasonably well (so you do not lose money to the use-it-or-lose-it rule).
You want the convenience of pre-tax payroll deduction for predictable expenses like contact lenses, dental work, or recurring prescriptions.
You are on Medicare and cannot contribute to an HSA.
You have a dependent care FSA for childcare, which is a separate thing from the health FSA and worth using if you have eligible childcare costs.
When the HSA makes more sense
You are enrolled in (or considering) an HSA-eligible high-deductible plan. See HSA-compatible health plans.
You are healthy in any given year and your medical spend is unpredictable. You build a long-term buffer.
You want a stealth retirement account. Many people pay current medical bills out of cash, leaving the HSA invested for decades. Reimburse yourself later (the IRS does not require reimbursement to happen in the same year, only that you have a receipt for the original expense).
You are self-employed and want a tax-advantaged way to fund healthcare. See self-employed health insurance options.
Mistakes that cost real money
Letting FSA money expire. The deadline catches busy people. Set a calendar reminder a month before year-end.
Funding both at once accidentally. If your spouse has a regular FSA at their job, your HSA contributions can be disqualified. Coordinate at open enrollment.
Filing for Social Security at 65 while contributing to an HSA. Social Security at 65 enrolls you in Medicare Part A retroactively, which ends HSA eligibility.
Treating an HSA like a checking account. Spending it down each year is fine but you miss the long-term growth benefit. Even leaving the balance in cash earns a little, and investing it earns much more over decades.
What to do next
Confirm whether your plan is HSA-eligible. If yes, fund the HSA before the FSA.
If you have both an HSA and an FSA option, the limited-purpose FSA (dental and vision only) is the combination that does not disqualify your HSA.
For your spouse coverage, check whether their FSA is regular or limited-purpose. A spouse regular FSA can disqualify your HSA contributions.
For more, see HSA-compatible plans and how to compare health insurance plans.
Sources
Frequently asked questions
Can I have both an FSA and an HSA?
Not usually. A regular health FSA generally disqualifies you from HSA contributions. A limited-purpose FSA (dental and vision only) can coexist with an HSA. A dependent care FSA can coexist with anything because it is for childcare, not medical.
Who owns the account?
You own the HSA. It goes with you between jobs and into retirement. The FSA is tied to your employer; if you leave, unspent money usually goes back to the employer.
Does FSA money roll over?
Most FSAs are use-it-or-lose-it. Some employers allow a small carryover (an IRS-set limit) or a grace period of a few months. The HSA rolls over indefinitely with no limit.
Which has better tax treatment?
Both reduce federal income tax. The HSA also lets the balance grow tax-free, and qualified withdrawals are tax-free. The FSA has no growth component because the money usually disappears at year-end.
