What are the tax differences between an FSA and an HSA?

Both let you pay medical costs with pre-tax dollars, but the tax treatment differs in important ways. A health FSA (2025 limit $3,300) reduces income and payroll tax, but it's generally use-it-or-lose-it each year, with at most a small carryover or grace period, and you don't need a specific health plan. An HSA (2025 limit $4,300 self / $8,550 family, plus $1,000 catch-up at 55+) requires a high-deductible health plan but is far more powerful: contributions are pre-tax, growth is tax-free, qualified withdrawals are tax-free, and the balance rolls over forever and is yours to invest. The HSA's triple tax advantage and portability make it a stealth retirement account. If you must choose, the HSA usually wins long-term; an FSA suits known near-term expenses. See wealthserene.com/tools/tax-strategies.