Health Savings Account (HSA)

An HSA is the only account with three tax advantages at once: deductible contributions, tax-free growth, and tax-free withdrawals for medical costs. It requires a high-deductible health plan, and unlike an FSA the balance rolls over forever. Used well it is a stealth retirement account — pay medical bills from cash, save the receipts, and let the HSA compound for decades before reimbursing yourself tax-free.