An HSA and a health FSA both cut your taxes the year you contribute. The difference shows up later: unspent HSA money invests and compounds tax-free, while unspent FSA money is mostly forfeited. Enter your numbers to see which account actually leaves you richer.
Sample input: Amount you will set aside this year ($): 3400, Your marginal tax rate (fed + state + FICA, %): 30, Medical you expect to spend this year ($): 1000, Years until you would spend the rest: 20, Expected investment return (%): 7
HSA advantage: 11007 (HSA comes out ahead)
The HSA wins by about $11,007. Both accounts cut your taxes up front, but the HSA lets the $2,400 you do not spend stay invested and grow tax-free (worth about $9,287 in 20 years), while the FSA would forfeit $1,720 of it.
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Both let you pay medical costs with pre-tax dollars. But an HSA is yours to keep, rolls over every year, and can be invested; a health FSA is employer-owned and mostly use-it-or-lose-it, with only up to $680 carrying over to next year in 2026. The HSA also has a higher limit ($4,400 self-only / $8,750 family in 2026 vs $3,400 for the FSA).
When you are confident you will spend the money this year on known costs such as braces, a planned procedure, or regular prescriptions. There is no forfeiture risk on dollars you spend, and an FSA does not require a high-deductible health plan the way an HSA does.
It computes each account first-year tax saving (contribution times your marginal rate), then adds the future value of unspent HSA dollars invested at your expected return, and subtracts any FSA dollars that would be forfeited above the $680 carryover. The HSA advantage is the difference.
Yes. HSAs require an HSA-eligible high-deductible health plan (HDHP). If your plan does not qualify, a health FSA may be your only pre-tax medical option. Check your plan HSA eligibility during open enrollment.