HSA vs. FSA (2026): The Complete Comparison — and What You Can Actually Buy With Each

Adam Z. Kawalek, MD

July 2, 2026 · 9 min read

If you have an HSA or an FSA, you are sitting on tax-free money set aside for health costs. Most people use only a fraction of it, partly because the rules are confusing and the two accounts sound almost identical. They are not. This guide breaks down how an HSA and an FSA actually differ, what the 2026 limits are, how to pick the right one, and the part almost nobody explains clearly: what you can really spend the money on. Plain language, current numbers, no fluff.

HSA vs. FSA: the short answer

An HSA (Health Savings Account) is yours for life. The money rolls over every year, follows you when you change jobs, and can even be invested. The catch is that you can only open one if you are enrolled in a high-deductible health plan. An FSA (Flexible Spending Account) is set up through your employer, has no health-plan requirement, and gives you the full year's amount on day one. The catch there is the deadline: FSA money is mostly use-it-or-lose-it, so unspent funds can disappear at year end.

A one-line way to remember it: an HSA is a long-term, portable savings account for health costs, while an FSA is a yearly spending budget you need to use up. Here is the full comparison.

What is an HSA?

A Health Savings Account is a personal savings account for medical expenses. To open one, you need to be enrolled in a high-deductible health plan, which the IRS defines each year by its deductible and out-of-pocket limits. Money you put in is not taxed, it grows tax-free, and you pay no tax when you spend it on qualified medical care. Because you own the account, the balance carries over year after year and stays with you if you switch jobs or retire. That combination is why many people treat an HSA as a long-term health nest egg, not just a spending account. The full rules are in IRS Publication 969.

What is an FSA?

A Flexible Spending Account is set up through your employer. You decide how much of your paycheck to set aside for the year, before taxes, and then spend it on qualified medical expenses. There is no health-plan requirement, so many people who cannot open an HSA can still use an FSA. One handy feature: your full annual election is available on the first day of the plan year, even though the money comes out of your paychecks gradually. The trade-off is the deadline, so it is worth planning your contribution around what you realistically expect to spend.

The differences that actually matter

1. Rollover vs. deadline

This is the big one. HSA funds never expire. FSA funds usually do. For 2026, an employer may let you carry over up to $680 of unused FSA money, or offer a grace period of up to two and a half months, but not both, and many plans offer neither. If your plan has neither, anything left at year end is gone. The 2026 FSA figures come from IRS Rev. Proc. 2025-32.

2. Ownership and job changes

You own your HSA. If you leave your job, it goes with you. An FSA belongs to your employer's plan, so if you leave, you usually lose whatever is left. That makes the HSA far more forgiving if your work situation changes in the middle of the year.

3. Who can open one

An FSA is available if your employer offers it. An HSA has a gate: you must be covered by a qualifying high-deductible health plan and generally cannot have other disqualifying coverage. If you are not on an HDHP, an FSA is likely your only option.

4. Investing and growth

Many HSAs let you invest the balance once it passes a threshold, so the money can grow over decades, similar to a retirement account. FSA money does not grow. It is a yearly budget, not an investment.

The 2026 numbers, confirmed

The IRS sets these figures each year. For 2026:

• HSA contribution limit: $4,400 for self-only coverage and $8,750 for family coverage, plus an extra $1,000 if you are 55 or older.
• Qualifying HDHP minimum deductible: $1,700 self-only, $3,400 family.
• HDHP out-of-pocket maximum: $8,500 self-only, $17,000 family.
• Health FSA contribution limit: $3,400 per employee.
• FSA carryover, if your employer allows it: up to $680 into the next year.

Sources: IRS Rev. Proc. 2025-19 for the HSA and HDHP figures, and IRS Rev. Proc. 2025-32 for the FSA figures.

Which one is right for you?

You often do not get a free choice, because the HSA depends on your health plan. But the logic is simple:

• Choose an HSA if you are on a high-deductible health plan and want money that rolls over, can grow, and stays yours. It is the stronger long-term account.
• Choose an FSA if your employer offers one and you are not on an HDHP, or if you have predictable expenses this year that you know you will spend.
• Consider both if it fits: with an HSA you generally cannot also have a standard FSA, but you may be allowed a limited-purpose FSA for dental and vision only.

If you are picking a health plan during open enrollment, the HSA option is worth serious thought. The rollover and portability are hard to beat for anyone who can qualify.

What you can actually buy with an HSA or FSA

This is where most guides stop short. Both accounts follow the same IRS definition of a qualified medical expense, so the eligible list is nearly identical, and it covers far more than copays and prescriptions. Common eligible buys include:

• Doctor visits, prescriptions, and copays
• Dental and vision care, including glasses and contacts
• First aid supplies, thermometers, and many over-the-counter medicines
• Sunscreen, menstrual products, and blood pressure monitors
• Therapy and mental health care

For the full list of what counts, the IRS keeps it in Publication 502.

Then there is the gray area: things that are good for your health but that the IRS treats as personal by default, like a gym membership, certain supplements, or an ergonomic chair. These are not eligible on their own. They can become eligible when a licensed physician documents that the item treats a specific diagnosed condition, using a Letter of Medical Necessity. If that is what you are after, start with our guide to what a Letter of Medical Necessity is.

Can you have both an HSA and an FSA?

Usually not in their standard forms at the same time, because a general-purpose FSA counts as disqualifying coverage for HSA eligibility. The common exception is a limited-purpose FSA, which only covers dental and vision. That one pairs with an HSA because it does not overlap with your medical coverage. If you want both, ask your benefits administrator whether a limited-purpose FSA is offered. These rules are summarized in IRS Publication 969.

A quick example

Say you set aside $2,000 this year. In the 22% federal tax bracket, running that $2,000 through an HSA or FSA instead of paying with post-tax dollars saves you roughly $440 in federal income tax, before any state savings. On that front, the two accounts are similar. The difference shows up at year end. If you put the $2,000 in an FSA and spend only $1,600, you could lose the remaining $400 unless your plan offers a carryover or grace period. If you put it in an HSA and spend $1,600, the other $400 simply stays in your account and rolls into next year, still yours, still invested if you choose. Same tax break going in, very different outcome on what is left over.

That is the practical case for the HSA when you can qualify, and the practical case for funding an FSA carefully when it is your only option.

Three common mistakes to avoid

A few traps catch people every year:

• Over-funding an FSA. Because it is use-it-or-lose-it, contributing more than you will actually spend can mean forfeiting the difference. Estimate conservatively.
• Forgetting the FSA deadline. Check whether your plan has a carryover, a grace period, or neither, then mark the date. Late December is when the scramble happens.
• Assuming anything health-related is eligible. General-wellness buys such as a standard gym membership are not eligible on their own. They need a Letter of Medical Necessity tied to a diagnosed condition, and even then the administrator decides.
• Passing up an HSA when you qualify. If you are on an HDHP and skip the HSA, you are leaving an easy tax break and a portable savings account on the table.

This article is for general information and is not tax, legal, or medical advice. IRS limits and plan rules change and vary by employer. Confirm the current figures and your plan's specifics with your benefits administrator or a tax professional.

Adam Z. Kawalek, MD

Board-Certified Physician · Founder, MedSlip · Cedars-Sinai · Johns Hopkins

Dr. Kawalek is a board-certified internal medicine physician with 15+ years of clinical experience. He founded MedSlip to give patients fast, affordable access to the Letters of Medical Necessity that make fitness and wellness spending HSA/FSA-eligible.