A health savings account is the only account in the US tax code with a triple benefit: contributions are deductible, growth is untaxed, and withdrawals for qualified medical expenses are tax-free. To contribute, you must be enrolled in a high-deductible health plan. The 2026 limits are $4,400 for self-only coverage and $8,750 for family coverage, with an extra $1,000 for people 55 and older. Employer contributions count toward the limit.
Contributions made through payroll also skip Social Security and Medicare tax, which even 401(k) contributions do not. For someone in the 24% bracket, a $4,400 payroll contribution saves about $1,056 in income tax and $337 in FICA.
The account belongs to you, not your employer, and the balance rolls over forever. That opens up a strategy: pay current medical bills from your checking account, keep the receipts, and let the HSA grow invested. Years later you can reimburse yourself for those old expenses tax-free, or after 65 withdraw for any purpose paying only income tax, like a traditional IRA.
The common mistakes are confusing it with an FSA (which expires), leaving the balance in cash instead of investing it, and spending it down each year when you could afford to pay out of pocket. If your health plan qualifies and you can cover the deductible, the HSA is usually worth funding before extra 401(k) contributions beyond the match.