Side by side, from the employer's chair
| HSA | Health FSA | |
|---|---|---|
| What it is | An individual account the employee owns | A group health plan the employer sponsors |
| 2026 limit | $4,400 self-only / $8,750 family (+$1,000 at 55+) | $3,400 per employee |
| 2027 limit | $4,500 / $9,000 | Published by the IRS in the fall |
| Risk if an employee spends early and leaves | None: only deposited money can be spent | Employer's: the full election is available from day one |
| Unused money at year-end | Stays with the employee | Forfeited, apart from an optional carryover (up to $680) or grace period |
| Claims substantiation | Employee keeps receipts; no approval needed | Administrator must substantiate every claim |
| COBRA | Not required for the account | Generally required |
| Leaves with the employee | Yes | No |
| Requires a specific health plan | Yes, an HSA-qualified plan | No, works with any plan |
Read down the table and almost every row favors the employer offering an HSA. The last row is the one that matters: an FSA works with any plan, while an HSA needs an HSA-qualified plan. That's why I treat this as a plan design question, not an accounts question.
The FSA risk most employers don't know they carry
Health FSAs follow the uniform coverage rule: an employee's full annual election must be available from the first day of the plan year, even though it's deducted from paychecks over twelve months. If an employee elects $3,400, spends it on a procedure in February and leaves in March, the employer covers the difference. You can't claw it back from their final paycheck.
Forfeitures run the other way: when employees under-spend, the leftover money goes back to the plan. Some employers see that as a wash. I don't, for two reasons. First, the losses land on your most expensive moments, often right as someone leaves. Second, forfeitures aren't a profit center you want; every dollar forfeited is a dollar an employee feels they lost, and they remember it at the next open enrollment.
An HSA has neither problem. Employees can only spend what has been deposited, so there's no front-loaded exposure. And nothing is forfeited, because the money was always theirs.
A worked example
Less to administer, less to get wrong
A health FSA is a group health plan. It needs a written plan document, runs inside a cafeteria plan, requires substantiation of every claim, is generally subject to COBRA, and must pass nondiscrimination testing. Most employers pay a third-party administrator a monthly fee per participant to handle it, and still field questions about denied claims and missing receipts.
An HSA is an individual trust or custodial account. The employee chooses what to spend it on and keeps their own receipts. The employer's job is mostly payroll: send pre-tax contributions to the custodian and make sure no employee goes over the annual limit. Employer contributions need to be comparable across employees, or run through the cafeteria plan, but that's a far lighter load than running a claims plan.
- No claims to adjudicate. The HSA custodian doesn't approve purchases.
- No year-end forfeiture process or run-out period to manage.
- No COBRA notices for the account itself.
- No uniform coverage exposure to budget for.
Employees value an HSA more
For employees, an HSA is the only account that's tax-free going in, tax-free while it grows and tax-free coming out for medical costs. Unused money rolls over forever, can be invested and goes with them when they leave. After 65 it works like a traditional retirement account for non-medical withdrawals. An FSA, by contrast, asks employees to guess their medical spending a year in advance and punishes them for guessing high.
That difference shows up in how people talk about the benefit. A $1,000 employer HSA contribution is money in an account with the employee's name on it. A $1,000 FSA election is a deadline. If you compete for engineers and other people who compare offers line by line, the HSA is the one they'll notice. And because the balance follows them, it keeps reminding them of your plan for years after they've enrolled.
The tax savings are the same, or better
Both accounts save the employer payroll tax when employees contribute through a cafeteria plan: 7.65% in Social Security and Medicare tax on every pre-tax dollar, below the Social Security wage base. Employer contributions to an HSA are also excluded from employees' wages. So moving from an FSA to an HSA doesn't cost the employer any tax savings, and because the HSA limit is higher ($4,400 vs. $3,400 for a single employee in 2026), employees who max it out shelter more pay, and the employer saves payroll tax on more of it.
One wrinkle: California and New Jersey don't recognize HSAs for state income tax, so employees there pay state tax on HSA contributions. Federal tax and payroll tax savings still apply.
When an FSA still makes sense
To be fair to the FSA: if your health plan isn't HSA-qualified, an FSA is the only pre-tax medical account you can offer, and it's better than nothing. Most traditional copay PPO and HMO plans fall into this group. The FSA's real advantage is that the full election is available on day one, which helps employees with a large expense early in the year.
The usual reason employers keep a copay plan is that a high-deductible plan pushes thousands of dollars of deductible onto employees. That's a real problem, and it's the one worth solving, because once the deductible is handled, the HSA wins on every other count.
Running an HSA with an FSA
An employee can't contribute to an HSA while covered by a general-purpose health FSA, theirs or a spouse's. If you offer an HSA-qualified plan, make your health FSA limited-purpose, covering only dental and vision, or drop it. A dependent care FSA for child care is a separate account and doesn't affect HSA eligibility, so keep it.
Spouses matter too. If an employee's spouse has a general-purpose health FSA at their own job that can reimburse the employee's medical expenses, the employee isn't HSA-eligible, even though your plan qualifies. You can't control another employer's FSA, so the practical fix is communication: ask about it at open enrollment, and explain that a spouse can usually choose a limited-purpose FSA or skip the FSA for the year. A short note in your enrollment materials prevents most excess contributions and the tax corrections that follow.
How to move your team from an FSA to an HSA
- Choose an HSA-qualified plan Pick a design that keeps out-of-pocket costs low, so employees don't trade an FSA for a large deductible.
- Fix the FSA Amend it to limited-purpose for the new year and deal with any carryover or grace period from the old one.
- Decide your employer contribution Seeding every HSA, especially enough to cover the deductible, is the single biggest thing employees will notice.
- Set up payroll Pre-tax deductions through the cafeteria plan, with limits tracked across employer and employee contributions.
- Explain it at open enrollment Lead with ownership: it's their money, it rolls over, and it leaves with them.
How Prescience handles it
With Prescience Diamond, every enrolled employee gets an HSA and an effective $0 deductible with simple copays, so nobody has to choose between the HSA's tax advantages and low out-of-pocket costs. Employees can still contribute their own pre-tax money on top. We sync contributions with payroll and track employer and employee deposits together, so nobody goes over the IRS limit.
