HSAs and FSAs both let you pay medical costs with pre-tax money — which means a real discount of 20–30% on everything you buy through them. But they follow very different rules, and mixing them up can cost you money.
HSA: Health Savings Account
- Only available if you're enrolled in a high-deductible health plan (HDHP).
- The money is yours forever. It rolls over every year and follows you when you change jobs.
- You can invest it, and it grows tax-free.
- Triple tax advantage: money goes in pre-tax, grows tax-free, and comes out tax-free for medical expenses.
- After 65, you can withdraw it for anything (taxed like a retirement account).
FSA: Flexible Spending Account
- Available with most plan types — no HDHP required.
- Use it or lose it. Most FSAs forfeit unspent money at year-end (some allow a small carryover or a grace period — check yours).
- The full year's election is available on day one, even before you've contributed it.
- It stays with your employer — you generally lose the balance if you leave mid-year (spend it first).
The One-Table Version
- Keeps rolling over? HSA yes · FSA mostly no
- Follows you to a new job? HSA yes · FSA no
- Can be invested? HSA yes · FSA no
- Requires an HDHP? HSA yes · FSA no
- Full amount available Jan 1? HSA no (only what's deposited) · FSA yes
Practical Moves
- If you have an FSA: set your election based on expenses you're confident about (glasses, prescriptions, planned procedures) — not hopes.
- If you have an HSA: contribute at least enough to cover your deductible if you can. If money's tight, anything helps — it's the most tax-advantaged account in the entire U.S. tax code.
- December with FSA money left? Stock up on eligible items — contacts, first-aid supplies, and many over-the-counter medicines qualify.
The Bottom Line
An HSA is a wallet you own for life. An FSA is a yearly spending pass. Know which one you have, and set the amount accordingly.