The open enrollment form you’re about to click through decides more than which health plan you’re on — it can lock in or lock out one of the most tax-efficient accounts available to you. An HSA and an FSA both let you set aside pre-tax dollars for medical costs, but they operate on almost opposite rules: one is yours forever, one generally isn’t; one requires a specific kind of health plan, one doesn’t; and picking the wrong one for your situation can mean forfeiting money you already earned.
For 2027, HSA contribution limits are rising to $4,500 for self-only coverage and $9,000 for family coverage. The 2027 FSA limit hasn’t been published yet — the IRS typically releases it in a Revenue Procedure each October or November, after most employers have already opened enrollment. That timing mismatch alone is worth understanding before you check a box.
Table of Contents
- What an HSA and FSA Actually Are
- The 2027 Numbers
- How the Money Behaves Differently
- The Catch With Each Account
- Which One Fits Your Situation
- Where Harness Fits In
- Putting It All Together
- FAQ
Key Takeaways
- An HSA requires a high-deductible health plan (HDHP); an FSA doesn’t. You’re only eligible to contribute to an HSA if you’re enrolled in a qualifying HDHP — the FSA has no such requirement and pairs with most other plan types.
- The 2027 HSA limits are $4,500 self-only and $9,000 family, per IRS Revenue Procedure 2026-24, with an extra $1,000 catch-up if you’re 55 or older.
- An HSA is yours permanently; most FSA balances are not. HSA funds roll over indefinitely and stay with you if you change jobs. FSA dollars are generally forfeited at year-end unless your employer offers a limited carryover or grace period — and even then, the leftover amount is capped.
- The 2027 FSA limit isn’t out yet. The IRS usually announces it in the fall, often after open enrollment has already started — plan your FSA election using the current $3,400 (2026) figure as your reference point and adjust if new guidance drops before your deadline.
- The “triple tax advantage” is unique to HSAs. Contributions go in pre-tax, growth is tax-free, and withdrawals for qualified medical expenses are tax-free — a structure no FSA offers.
What an HSA and FSA actually are
A Health Savings Account (HSA) is a tax-advantaged account you own individually, available only if you’re enrolled in an HSA-qualifying high-deductible health plan under IRC Section 223. Contributions reduce taxable income, grow tax-deferred, and come out tax-free for qualified medical expenses. There’s no use-it-or-lose-it — a balance simply carries forward, year after year, employer after employer.
A Flexible Spending Account (FSA), created under the cafeteria-plan rules of IRC Section 125, is owned by your employer’s plan, not by you. You elect an annual contribution, it’s deducted pre-tax from pay, and you draw it down for eligible medical (or dependent care) expenses during the plan year. Unlike an HSA, an FSA requires no specific health plan — it’s available regardless of whether you’re in a high-deductible plan, a PPO, or an HMO.
The dividing line that matters most: can you get an HSA at all? That depends entirely on whether your plan option meets the IRS definition of a qualifying HDHP. If it doesn’t, the FSA (or nothing) is your only pre-tax option for routine medical costs.
The 2027 numbers
For 2027, per IRS Rev. Proc. 2026-24:
- HSA contribution limit: $4,500 self-only coverage, $9,000 family coverage
- HSA catch-up (age 55+): an additional $1,000, on top of either limit
- HDHP minimum annual deductible: $1,750 self-only, $3,500 family
- HDHP maximum out-of-pocket: $8,700 self-only, $17,400 family
If you’re enrolling in a plan that runs on the 2026 calendar year rather than 2027, the applicable HSA limits are $4,400 self-only and $8,750 family, per Rev. Proc. 2025-19 — worth checking which plan year your open enrollment actually governs.
The FSA side is murkier. The 2026 Health FSA limit is $3,400, with a $680 carryover for plans that permit it. As of this writing, the IRS hasn’t released the official 2027 FSA figure — that announcement typically lands in a Revenue Procedure in October or November, which can be after your employer’s enrollment window closes. If you’re electing an FSA amount before the 2027 number is public, use the 2026 figure as your anchor and watch for updated guidance.
Worked example (illustrative). Jonas and his wife are choosing between a PPO with an FSA and an HDHP with an HSA for 2027. Their projected routine medical and dental costs are $3,850 for the year. Under the FSA path, they’d elect close to the full 2026-equivalent limit and risk forfeiting anything past the $680 carryover. Under the HDHP-plus-HSA path, they could contribute up to $9,000 as a family, using $3,850 for expected costs and letting the remaining $5,150 grow tax-free — assuming they’re comfortable with the HDHP’s $3,500 minimum deductible before coverage kicks in.
How the money behaves differently in practice
- Portability. An HSA moves with you — job changes, career breaks, retirement. An FSA generally ends when your employment does, subject to COBRA continuation rules.
- Investment growth. Most HSA providers let you invest balances above a threshold in mutual funds once your balance clears a minimum; FSA funds simply sit as a spending balance with no investment option.
- Eligible expense timing. With an FSA, your full annual election is typically available to spend from day one of the plan year, even before you’ve contributed all of it through payroll. An HSA only holds what’s actually been contributed and vested to date.
- What happens to unused funds. HSA: nothing happens — it stays yours indefinitely. FSA: generally forfeited at plan year-end unless your employer offers either a grace period (typically up to 2.5 extra months to spend it) or a carryover (a capped dollar amount, $680 for 2026, that rolls into the next year) — a plan can offer one or the other, not both.
The catch — what each account requires (and risks)
The HSA catch: you have to be in a qualifying HDHP to contribute at all, and that plan design means higher out-of-pocket exposure before coverage kicks in — up to $8,700 self-only or $17,400 family for 2027. If your medical spending is predictable and moderate, the HDHP-plus-HSA combination may cost more in a bad health year even as it saves more in taxes.
The FSA catch — the classic “use it or lose it” problem. Overestimate your spending and elect too much, and anything beyond your plan’s grace period or carryover cap simply disappears at year-end; it doesn’t roll into your paycheck or come back as a refund. What’s actually predictable enough about your medical spending to commit to a number in October for costs you’ll incur next year? For many people, not much — which is exactly why overfunding an FSA is a common, avoidable mistake.
The dependent-care wrinkle. A separate Dependent Care FSA exists for childcare costs, capped by statute and not indexed for inflation — worth knowing if enrollment bundles it with the health FSA decision. If you’re planning around childcare alongside coverage, see our guide on tax and financial planning for new parents.
Which one fits your situation
- Predictable, moderate costs and low tolerance for high deductibles → an FSA paired with a traditional (non-HDHP) plan may fit better.
- Generally healthy, comfortable with a higher deductible, interested in long-term tax-free growth → an HDHP-plus-HSA combination often wins, especially if you can pay routine costs out of pocket and let the balance compound.
- Anticipate a job change soon → the HSA’s portability is a meaningful advantage; an FSA balance is generally use-it-or-lose-it if you leave your employer mid-year.
- Want to treat the HSA as a retirement-adjacent account → with no use-it-or-lose-it rule and investment options often available, some people deliberately underspend their HSA and let it accumulate for future medical costs, including in retirement.
Before locking in an election, revisit your broader financial plan and how idle cash is allocated across your accounts generally — the same liquidity-versus-growth tradeoffs apply here.
Where Harness fits in
Open enrollment gets treated as a five-minute form-fill, but the HSA-versus-FSA choice interacts with your deductible tolerance, your employer’s benefits design, and your broader tax picture — exactly the kind of decision worth a second opinion. Harness connects you with tax advisors who can walk through your health plan options, projected medical spending, and overall financial plan before you submit your election, not after.
Putting it all together
Three things decide this choice: whether your available plan qualifies as an HDHP (which gates HSA eligibility entirely), how predictable your annual medical spending is (which determines FSA forfeiture risk), and how much you value portability and tax-free growth versus immediate full-balance access. Get those three answers before your enrollment deadline, not after the first paycheck deduction hits.
Frequently Asked Questions
Can I have both an HSA and an FSA at the same time? Generally no, with one exception: an HSA can typically only be paired with a “limited-purpose” FSA covering dental and vision only, not a general-purpose health FSA, which usually disqualifies you from HSA contributions for that period.
What is the 2027 HSA contribution limit? $4,500 for self-only coverage and $9,000 for family coverage, per IRS Rev. Proc. 2026-24, plus a $1,000 catch-up if you’re 55 or older.
Has the IRS released the 2027 FSA contribution limit yet? Not as of this writing. The IRS typically announces it in a separate fall Revenue Procedure, sometimes after open enrollment has begun. Use the current $3,400 (2026) figure as a reference until the 2027 number is confirmed.
What happens to unused FSA money at the end of the year? It’s generally forfeited, unless your employer’s plan offers a grace period (often up to 2.5 extra months to spend it) or a capped carryover ($680 for 2026). A plan can offer one of these, not both.
Does unused HSA money expire? No. HSA balances carry over indefinitely with no deadline to spend them, and the account stays with you even if you change employers or health plans.
Do I need an HDHP to contribute to an HSA? Yes. HSA eligibility requires enrollment in a qualifying high-deductible health plan meeting the IRS’s minimum deductible and maximum out-of-pocket thresholds for the year.
Is HSA money taxed when I withdraw it? Withdrawals for qualified medical expenses are tax-free. Withdrawals for non-medical expenses before age 65 are generally taxable and may incur an additional penalty; after 65, non-medical withdrawals are taxed as ordinary income but avoid the penalty.
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